Attempt at Dart Thrower down picking motion

ive been in need of help with my down picking for a long time. My goal is to be able to play master of puppets up to tempo with the proper down picking as needed. The closest i can get is roughly 80 percent speed on guitar pro. I am currently just working on adapting the dart thrower motion and down picking on the bottom string. i would really appreciate some direction on what i am doing right and wrong and the best ways to implement and practice this new technique. Thanks so much