BrownBomberWhen I learned them, I did the same thing. In fact, I learned Underflip before I landed the Lincoln. For me, I focus on driving the shoulder that im lifting (I spin left so its my right) forward, especially at the beginning of the rotation. It feels like an over emphasized cork 3 to me. Really a fun trick once you figure it out. Good Luck!
same, i learned underflips too, the jump throws you pack so make sure to pop a bit more forward and dont turn your head... resist doing the 180 to switch!!