All right! I had a concern before I started this project, but everything was working out so well I set that concern aside. I probably should have listened to my instincts.
Melamine is a wonderful material. It has very low friction, so objects can move around any way I want them to. Great. Glue won't stick to it very well, either, so anything that gets splattered on it will clean up with little fuss.
But, even though I reinforced the top with a glue line between two layers of hardboard, the material began to flex a little. I added a row of screws along the edge, something I had determined was a bad idea some time ago, and the top was still developing some very slight high spots. Tightening the screws meant flaring out the edges of the counter-sunk holes they were living in, but I tightened two particular screws and one of them started plowing through the bottom of the hardboard.
At that point I threw up my hands. And then I threw out the melamine.
I am building a new top over the same substrate. This top will be thicker, so I'll have to raise the level of the router plate, but that's not really an issue. I'm building it out of MDF, the same material that makes up most of the table already. It's very hard and very flat. And there's no real reason to attach it to the substrate. It will just sit there and there will be no forces applied to cause it to warp out of shape. Right now it is dead solid flat, sitting where it will live from now on.
This weekend I will rout out the hole in the middle, using the old top as my template. The jig I built would do the job just fine, but it will be simpler to align the new top with the old because they are exactly the same size.
I promise to have photos ready very soon!