Mark,

Just looked at the pics you posted. Interesting the way they did that but
how in the hell they expect it to be flat for the entire length is beyond
me. I would call Jet and tell them about about bad that fence is and ask
them to send a replacement - whether it's under warranty or not. That is a
design or manufacturing flaw and they probably already have had so many
complaints that they have a fix for that. Squeaky wheel gets the grease....

But if you're determined to make this work, then I wouldn't place a screw
hole in the area of the clips because you need to countersink it on the face
side and there's not eneough thickness for that. So place the first screw
nearer the end, about an inch away from the clip. Same for the other end.
Place at least 3 or 4 more in between.

Those are self-tapping screws it looks like and that is powder-coated paint,
so as you said, those screws will be tough to get out but they will come
out.

Before you go to far - measure how far out (pluse and minus) the metal fence
is from end to end. If there is a big transition from the high to low spots
you will need to either lower the high spots or raise the low spots by
shimming or use a fence face material that will not deform and bend as
easily as the UHMW.

The suggestion of using Baltic Birch is good but finding it may be a trick
and a 5x5 sheet is a bit pricey if you don't have a need for the rest of it.
There are other ply's but are they available in your area is the question.
Have a cabinet shop around that may sell you some cutoffs?

You could use 3/4" MDF and laminate it with Formica as another idea. It's
inexpensive and flat - just be mindful of the dust and don't use your best
blade to machine it.

Weather permitting (it's an unheated shop), I'll take a pic or two of mine
so you can see exactly what I'm suggesting.

Bob S.