Do you guys increase the diameter of the holes in the stock that the screws go through to attach the floorplate to the action? I seem to remember reading that after you glass bed the stock, you want to run a drill through the holes in the stock to enlarge them so the action screws are, in a sense, free floated.

Yes. The screws should be clear. And actions like Howa, Ruger, Mauser and similar should have clearance at the back of the tang. I just put masking tape around the tang and a very small amount folded under the tang.

The M70 should have clearance behind the square thread section that is under the tang.

Rem 700 and Wby Mark V tangs sit completely on top of the stock and so need nothing special.

In short, only the recoil lug should have bedding behind it.

How large should you enlarge the screw holes?

I have never measured what I do but at a guess the I would have the hole about 1/16" or so bigger in diameter. But even if it was only a few thou that would be OK.

I also put a few wraps of masking tape around the screw. The reason being the screws can be out of roud, especially when they have been buffed a few times with a steel buff to remove epoxy. If the screws are out of round then they can be very difficul to get out even though there is release agent on them.