as long as the ball driller you use knows to drill the finger holes deeper to remove the excess finger weight, then you should have no noticable changes in ball dynamics. I've had all four of my balls done with the VISE IT, and i've had no problems with ball reaction.

In a non-technical test, I had laid out a ball with a differential of .050. I placed the pin above the fingers and drilled without anything other than finger inserts and a thumb solid normal depth (fingers 1 3/4" & thumb 2 1/2").
After placing a Turbo Switch Grip in, the ball reacted approx 5' earlier and the flare was increased 1/2", with the width between the flares approx 1/16". This is off the top of my head, as I did this almost a year ago. But it does increase the overall diff as well as lowering the RG. You are placing a giant weight hole away from the pin.
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Formerly BrunsRico