I have local bowler who uses his thumb but has a very similar track. If uses label leverage or any conventional righty drill he clips the fingers as it flares. Now is using a near lefty full roller layout that stays on the right side of ring finger and thumb. I have never seen any one turn the ball this much with a thumb in and track this high, and do all this with a smooth release. His current drill does not give him very good carry but is quiet. I wonder if he used a conventional 7 o clock righty full roller drill if it would bring the track between instead of a lefty type track......same dilema here in Ohio, Alzgarvin