Originally Posted by wakeX2wake
using a hole saw bit in reverse w/ nothing to guide you... the bit wanted to jump each time you made contact w/ the fiberglass b/c there was already a big hole there where the other courtesy light was so there was nothing for the auger or "guide" bit to hold to to keep the bit perfectly straight
Depending on how much larger the new hole would be, I'd have done one of 2 things:
1. If the new hole was large enough to allow for a screw head inside the diameter of the new hole, you can screw a strip of plywood behind the old hole for the pilot bit to bite into.
2. If the new hole was just slightly larger, you could make a template (cut the hole in a scrap of smooth plywood) for the hole saw to run in and clamp/ tape/ hold it in place.