I'm trying to draw up an Epidemic with the pin about 4 1/2" from PAP and keep the MB in a strongish position. The pin is 4" from CG (inline). On this ball I'm trying to avoid a balance hole so it seems the MB will be around the thumb hole. Top is 3 3/4oz so I'm trying to keep the CG pretty close to center of grip. Is there an issue drilling the thumb hole in or near the MB?  How will it effect the ball?

Thanks for the reply. What would it do the ball reaction/performance if anything?

Drilling into the MB will make the ball have a symmetrical type of reaction. It will make the ball read friction and smooth the backend. Now, this doesn't mean the ball wont hook, because it will. The overall reaction will be an arc rather than a flip. A friend of mine drills out his MB because he likes the reaction and it doesnt hurt that he avges 230+. Key is to just treat it like a symmetrical. MB in the thumb, anything below 3.3/8" will reduce flare.