I would never use this what I would recommend and what Pete Shepley would too is lock your elbow because you never know how much exactly you bend your elbow so you could never be 100% consistent if you don't know exactly how much you really bend you elbow and turn your elbow up to avoid hitting your arm with the string
I would never use it personally. My suggestion is to practice and practice some more. My opinion is that you should NOT lock your elbow.
It is a good product as it helps promote good form but unfortunately only eliminates torque in one direction. What I use is a Square Up rear sight. I do not believe locking your elbow will eliminate torque anymore than an open hand grip.
