With 1/4 oz. thumb weight and 3/4 oz of side, you can remove 1 1/4 oz. of thumb and still have 1 oz. of finger and be safe.
Removing 3/4 oz. of side or more and you can go so far as 1 oz. of negative side and still be safe.
That's a lot of core removal.
I put the MB/PSA in the thumb hole of a Solid Lev RG, with the CG more than 1" left of the pin-PSA line. I wound up with 5/8 oz of negative side weight and a bunch of finger weight. The PSA in the thumb hole increased dynamics so much, even with the pin OVER the middle finger (I'm a righty), the ball made a major freaking left turn.
Do not be afraid of using maximum negative side and thumb or finger weight. 3 oz. of top or bottom weight might make a tiny bit more difference, but the likelihood of that is miniscule.
The proper amount of core removal is of paramount importance, not final static weights.