Bob Mill wrote:
That's kinda was I was thinking, but here's a dumb question. Since
they old insert clipped into the table, but plywood insert isn't going
to be able to do that. How do you guys secure your homemade insert
into the opening?


Mine just sits in there on the four 'feet' that protrude into the
opening. You could wrap some tape around the perimieter of your
existing a few times so that when you rout it will be slightly
oversized. Then sand for a snug fit.