Ben wrote:
I've got the 10" Delta Contractor saw, Platinum Edition with the Unisaw
and the 30" extension. I'm finding that the extension, which is really
little more than piece of countertop, tends to warp and simply won't
align flush with the table top--it tends to ride up at the outfeed
side.

snip

Something doesn't add up.

I have the same package for which I added a mobile base consisting of a
couple of weldments that bolt together to form a unit base.

System works just fine.

I'm in SoCal and keep the saw outside covered by a tarp which some years
means a bunch of rain, like 34" YTD, this year.

It's been that way for 5 years. So far, so good other than the melamine
edge banding which long ago too a hike.

Every so often, it's time for some WD40 and 150 grit on my ROS, followed
by some wax but that is NBD.

Got any idea what is causing the warping?

BTW, one of these days, will replace that piece of melamine covered MDF.

When I do, will use a piece of "B" grade, 13 ply, fixture grade material
covered with a plastic laminate on top and having ALL other raw surfaces
sealed with a couple of coats of laminating epoxy.

That puppy will still be here when my grand kids are gone.

HTH

Lew