I really am a bad bowler. I do so many bad things and have so little true important knowledge about the game that its embarrassing.
Ball fit is one of those things that I don't understand. Angles, pitch, span, not withstanding, I don't know what good fit is. Should it feel tight on the fingers should it be loose or comfortable versus effective. All that said I have been fiddling with fit loosing and gaining weight its hard to maintain a constant.
My wife, not a, "bowler", was trying to find me a gift and she came across these thumb socks. Once I got used to them, its harder to hold the ball,another issue,I realized that because I was hanging in the thumb,not properly clearing the ball I was tracking over the thumb. With the sock I clear and no track without sock I hang and track over the thumb shot after shot. And because I had to tighten my thumb to control the ball I have learned the thumb should be tight. A tighter thumb also makes it harder to squeeze the ball. Wow thanks to my wife, who again shows she is smarter than I even in an area she isn't involved in.