Nail'd

If you have not earned this after completing the tournament mode, I recommend doing Simple Race on Dambuster with Boost Madness mutator turned on. All of the opponents are still grouped together at the first jump increasing your odds of landing on one. Also, after you land, you can restart the race and try it again and you will not lose any you have already earned. I did it this way and it took me about 10 minutes to earn the 6 that I needed for the trophy.