[Richard in Florida]

Originally Posted by Mike B

I took a piece of flat bar and "eyeball" centered it and tacked into place on the "backside" of the hole, then took a scribe compass to find my center of the hole, and drilled through for a holesaw bit.

I really like this idea. A holesaw brings neatness, and neatness counts. On top of that, here's another opportunity to buy a new tool!