I have a couple of balls that I had the thumbhole plugged and redrilled to try a shortened span. I decided to swith back to my old span.  When the pro shop switched me back, there was still plugwork showing even after trying to cover-up with a 1 3/8 inch slug. Now I can live with a plugged ball if a good job was done to match color, however my experience is not the case.  A 1 1/2 inch slug will cover up all plugwork and the existing 1 3/8 slug once all is drilled out.  How much should I expect this to change static weights.  My thumb hole size is 59/64.  Will the 1 1/2 slug put more emphasis on thumbweight or is it the slug so light that it gives me more finger weight?

The big issue which could change the weights is how much of the denser core material you catch when drilling for the slug.