Yes it's possible. . . Depending on how far out the CG is. And the size/depth of the holes being drilled into it. Taking into account that side weight is only one of the static weight measurements. Depending on where you put the holes . . . You may need a balance hole due to finger/thumb being off. If you have a layout in mind . . . Lay it out and take a pre-drilling static weight. If you're looking for something legal but tweakable . . . Try to get it around 3/4 positive side and 3/4 thumb, if you can't get the thumb weight close, you can always drill the fingers deeper.

On the balance hole . . . It ALL matters. If you want it stronger or weaker . . . The location, size and depth are all factors. Don't forget about surface prep too:)

 I agree that it can be done, within limits, but your question makes me want to ask you, "Why do you ask"?

 Is it your desire to drill a ball with a label shift, but within "legal" limits, try it out, then alter the reaction (if desired) later?

 If so, take a GOOD look at what tommymo has told you. In his post, he tells you that you can strengthen, OR WEAKEN, a balls reaction with a weighthole, depending on where you put it, how deep you drill it, or how big you drill it.

 I also believe his remark about wanting to end up with thumbweight is if you are definitely planning on using a flare increasing hole, because doing so will allow you to put the weighthole in a very strong position.  I could be wrong, but check with him first before you drill it.

 If I am wrong, then I have misunderstood his premise, and apologize for my presumption.