I use the pinch system only because I have tendency to over control using only my thumb. With that being said, I do use my thumb on the throttle stick. I think I do that because of having the trainer switch above the left stick. That way I can pull the trainer switch with my index finger and keep my thumb on the throttle. I'm working with an older student that if he tries the pinch technique he squeezes that hell out of the sticks and his fingers go numb. SOOOOO, he uses his thumbs.