I heard a few bad stories about the switch grips, so I decided on the Vise IT system, have it in all of my balls, and love it. Very sturdy, easy to switch back and forth with no problems.
The only negative on Vise I have, isn't even with the company.
Problem A: People with that use a lot of rosin or easy slide on their thumbs, can create a build up in the bottom of the mechanism. So if you do use that stuff often, I recommend you keep it clean to prevent any problems. I haven't had any problems as I use the stuff very lightly here and there, but I've heard of one guy who had enough "caked" into the threads that the slug locked into place and wouldn't come out. But even in his case, he took it to the pro shop, and they used a soft wood insert, and some channel locks to budge the slug, took it out, cleaner it, and it worked great again.
Problem B: Is with the driller. I haven't had it happen to me, but a guy in my league had a similar span to me, and allowed me to put my thumb in his ball to see how I liked his ball, but there was a slight difference in the... I guess... degree of installation? Meaning that my thumb was slightly rotated in his ball when in the "locked" position, so it wasn't perfectly flush. It was slight, and again, even in this situation, you shouldn't be rolling over your thumb anyways, but try to use the same driller each time, or at least bring in your other balls with the system, so he can align them to match.
So, only 2 cons, and like I said, neither of them are directly related to the company, or design. I highly recommend the system, it's great having 2-3 separate feeling thumbs, that I can switch back and forth to, depending on how hot/cold the alley is, due to hand swelling/shrinking. I don't ever have to worry about playing with tape in my thumb hole anymore.
Cost $25 initially to be installed, which included the receiver in the ball, and my custom slug. Each ball after that was only $10-15 just for the receptacle. And I can have a new thumb fit anytime I want for $10!
Here's a thread I wrote in hammerforums with pictures:
http://forums.hammerbowling.com/showthread.php?t=10458--------------------
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