I would suggest a video camera and tape your practice sessions from behind.side and front ( at a slight angle so you dont shoot the camera)

I done that to one of my students yesterday who claimed he did not punch the trigger and grab the bow at the shot.

Should have seen the look on his face when I played it back through a big screen TV.

I am not a big fan of this open hand grip style as it does tend for torque specially if your palm is touching the grip.

IMO the best way to grip is with your thumb and index finger touching the riser and the rest of your knuckles at a 45 degree angle away from the grip.
With the back of the grip in the meaty part of your thumb and remember the old saying never cross the life line.