I'm currently at 3/16 reverse and feel like I have a hard time keeping the ball on my hand throughout the swing and at release.  I just had a new snug 3/16 reverse, a 1/16 reverse, and a 1/16 forward switch grip thumb drilled so I can experiment.  I hung up on all of them until I opened the top of the thumb a bit and added bevel.  The 3/16 reverse required a minimal amount and the 1/16 forward required a little more. Nothing extreme but I did need more so that I could be confident I would get out of the ball.  Now that I can clear the thumb it feels like the ball comes off too fast at the bottom.   I do like that the ball stays on my hand better throughout the swing.

This is the most forward I have ever been.  Until I drilled my new equipment I was usually at 3/8 reverse

Should I go more forward and just open the top and bevel the thumb until I can clear? 

Charlest,

You have a point.  I guess that is an important question.

What is shaping type bevel versus release bevel.

I still remember the release tips told to me by Mo Pinel which I thought were awesome and very helpful....I am surprised he allowed any bevel as he is quite a proponent of proper fit also.

Note personally I use a modest amount of bevel.....but I don't try using extreme forward in relation to my comfortable span....to cause some of the thumb problems talked about by many on this site...

Regards,

Luckylefty
PS recently a well known amateur star and driller was talking to me extensively about bevel I am surprised these "other" smart guys think it is important...

Back when bowlers used "rocks", there was method to get the hand flat on the ball and comfort for long formats.  It was called "teardropping" the holes (including the fingers).    This was beveling the gripping side of the holes until the hand was flat on the ball.     Under pitch on all holes was common then.  You had to start with a longer span to accomplish this.  Was really comfortable. 

A forward pitch on thumb generally needs some bevel.   To control the bevel use a 1 1/4 or 1 3/8 drill bit.  The bevel on the other parts of the hole don't matter as far as grip is concerned, just helps with quicker thumb release.

Darn, posted and didn't immediately start an argument.  I must be slipping, so.....

Urethane thumb slugs are a must today.  This "reactive" stuff  does not work well with skin

Too many people are having thumb problems!!!    Must be a lot of "ball drillers" out there.

I think there are many who just don't know how to hold and release a ball.   A big percent of people just need lessons on holding and releasing the ball.  Remember, most all of the thumb issues are caused by improper fit and release (it's not your thumbs fault).   The fixation on using tape and inserts is just  not having a proper fit  or learning how  to hold and release.

Bowled for many, many years with no thumb or release problems, so it is possible for most people to bowl without excessive use of tape, thumb inserts, etc.

Last shot, get rid of "Iron Maiden" type wrist supports. These are a curse to bowlers.  If you persist in using one, at least get your ball fitted while wearing one