Puyo Puyo Tetris 2

To perform a Back-to-Back Tetris, you need to first start a Tetris Marathon game and stack all the blocks without leaving any spaces except for one column to drop a straight blue piece into for a 4 line clear and then do it a second time without clearing any other lines to record the "Back-to-Back" Tetris. Do this 50 times and pop goes the achievement!

Here is a video of my setup, you see the Back-to-Back pop up on the screen after the second (and third and fourth and so on) Tetris line clear: