As a thumb draw user, that's not a choice made lightly. Expect to give up the shelf, since you'd shoot from the other side of the bow due to the torque imparted. I draw a solid 38" to the earlobe with thumb, and it is a comfortable, natural draw due to Marfan syndrome. If you really wanted to relearn how to shoot I could set you on your way with a thumb draw, but those three inches aren't going to be magic, as others have said. A bow built to your draw would be better, in my opinion.