Kinect Joy Ride

You'll want to go to "Gorge 3" for this achievement.

The key here is to do TWO stunts at once, which in turn will give you two stunt medals. By doing this, I was able to get 9 total platinum seals. A platinum seal is defined by 3 platinum stars with a gold circle and a platinum circle surrounding that.

For this achievement, I recommend the front flip-spin stunt (moving your body left or right while simultaneously leaning forward). I used this move to get my platinum seals.

While doing the move, don't worry about landing. Just hold the move as long as you can. The game will automatically stop your trick and land you safely. So never prematurely stop a stunt because that can cost you a platinum medal.

Additionally, you will want to make sure that you are also snagging a bunch of hour glasses to add more time to your clock. So make sure you're not just going up and down the ramp. Add a little angle when going up and that should allow you to hit more items.

The most difficult part of this is gaining enough air. You will need a lot of air! The key to this is boosting just as you exit the curve and enter the middle of the half pipe. With a full boost, this should give you a lot of momentum.

It will take you a while to get the technique of stunting then switching to boosting pose, but once you do then you will get this achievement with ease. The more important thing, though, is time. The more time you get, the more time you will have to gain more air. The more air you have then the longer you can hold your stunt.

Note: Item platinum medals do not count towards this achievement. Only STUNT medals.

I'm using a bit from Perpalicious solution above and sort of summarizing suggestions from the comments on that solution and adding my own experience.

Here's how I pulled it off

Map: Gorge 2 (Amateur)
Players: 2 (In other words, use the help of a friend)

1. Your friend is there only to grab hourglasses to extend your "race" giving the one who is going for the achievement more time to do jumps.

2. How to get the 7 Platimum-medals:

- A platinum medal has 3 small stars in the middle and that is what you need to look for and you get them for spinning enough times with your car in the air
- Speed boosting came at different times for me since I sometimes messed up charging the boost while in the air, being concentrated on the spinning. Therefore, I sometimes started boosting as I landed and then fired off the boost in the middle of the halfpipe. So, it should happen between the white line where you land and the middle of the half pipe, going for the opposite side, depending on when you started to charge it. Try it out and you'll notice when you reach the highest.
- A lot of the comments give different suggestions on how to lean in order to spin the car to get platinum medals. One thing is for sure: You need to lean in two "directions" to make two different spins happen, hopefully giving you two platinum medals per jump. If you drive in to the jump with a slight angle instead of just straight, you will hit some hourglasses as well, which is crucial.

I chose the following: upper body twist to the right and backwards. In other words, I hold the wheel like I'm driving, twisting the whole body(legs and hips as well), facing to the right while I slightly bend my back backwards. That registered better than leaning forward, at least for me, and also registered as me twisting my upper body, though I actually spun my WHOLE body to the right. You'll see if it is the correct two spins when the medals start saying "360" etc, and "Barrel Role". Start leaning immidiately when the jump starts!

Consider this: The time I got the achievement, I didn't get my first platinum medal until my forth jump since I didn't have enough momentum until then. Some comments say "start doing spins at the third jump", which you can do but the momentum might not be enough. You should be touching the coins above the glass to be high enough to get 2 platinum medals in that jump.

It took quite a few tries but finally I had a good run with:
1. A good stance that registered two different spins
2. My buddy hitting a lot of hour glasses
3. 6-8 jumps in total, netting me the seventh medal in the last jump with time run out

Hope this helps and hang in there... I wanted to murder someone too, believe me.

/ NekoHenke

This achievement can be a killer! My back is so sore after trying this for more than 10 hours straight. The other guides are helpful but they missed to mention one crucial part of making it. It might be obvious but you really have to make sure the car is going straight when you start doing your tricks. If you are going a bit sideways you wont have enough time/height to do enough tricks.

So here is how I got this achievement!

Map = Gorge 2

From starting position you will go down a ramp! Have your arms straight in front of you and pull them back to charge your boost and use it before the first ramp. Now towards the first ramp you want to go a bit to the left to increase your chances to get some hourglass for 3 seconds extra on the clock. Getting some of these during your first 4 ramps will help a lot. immediately after you are jumping up your first ramp, pull your arms back and hold them in that position. That should charge your boost up again.

When you are reaching the bottom of the ramp you will see a white line! You want to use your boost from now on each time you are at the white line when you reach the bottom of a ramp. If you fail to charge your boost, try to charge it before it is too late. It can be ok to use it later but it needs to be fully charged and activated before you reach the ramp going up.

As soon you have used a boost move your hands back so it will hopefully charge. Continue getting hourglasses if you get lucky and gain some height after each ramp until you have going up a ramp 5 times. I started doing tricks on the 5th one and on the 5th one you really want to focus on making it so your car go straight towards the ramp and not sideways. Because that is the key to success! Even if you use the boost at the right place, you will not have enough height to get enough tricks if you are not going straight.

So on the 5th ramp up you might get one platinum star! I don´t think I got one here but I am not sure.
But I know that you have time for at least 8 ramps if you get enough hourglasses and good height for some more hourglasses that are very high up. (I might have done 9 ramps when I managed to get the achievement).

Now when you are doing the tricks you want to be quick moving your hand back to the charge position after you have used a boost. Then turn your body left or right to make the car spin in that direction. Keep your arms in front of you so your boost hopefully charge. But when you turn your body left or right you want to have the arms facing the side of you so you kind off twist your body. Also sometimes the boost won´t charge and you have to just focus on getting enough tricks and when you land after the ramp you have to quickly charge it and use the boost before reaching the next ramp. And again, make sure that your car is going straight!

After you have twisted your body with arms pointing left or right you want to lean forward immediately for the other trick as soon you see your car start spinning so it does both tricks at the same time. (So it will be like you are leaning towards the tv but your stomach is facing either left or right direction with the arms pointing at the same direction. (Yeah, it hurts to attempt this for 10 hours straight). Now try to maintain this position so you see both trick meters for spinning the car and flipping the car go up. You want it to reach 3 silver/platinum stars with a gold circle around it and silver/platinum circle around it. (The one for items does not count towards this achievement so you want to see three circles each time. Each time you managed to completely fill one of the stunt circles with the 3 stars you have managed a platinum for the trick and you need 7 of them in one go.

So on the 6th, 7th and 8th ramp you likely need to get two platinum for the tricks. And if you manage that and have 6 platinum so far you might be lucky and have time for a 9th ramp.

So to summarise:

1. Make sure to go straight towards the ramp when you are moving towards your 5th ramp and onward.

2. Make sure to aim to use the boost when you are landing after a ramp at the white line.

3. Try to twist your body and then lean forward to get two tricks at the same time and with good height on each ramp after the 5th you might make it.

This was a very difficult achievement for me! But the difference for me was when I figured out that I wasn´t moving straight towards the later ramps.