I bought a Grizzly G0512 - 6" x 80" Edge Sander w/ Wrap-Around Table years back and it had some issues.
The press board Table top with Formica lam. was not flat.
The angle brackets to hold the table top to the machine were warp because of the long slot punched in it.
So I got some 1 x 1 x 1/8" angle aluminum, carriage bolt 50 I think, nuts.
I drilled the holes and bolted the angle alum. to the bottom. look close on the 2nd picture and you can see some.
For the warped angle bracket I welded a 1/4" x1-1/2" to make it like angle iron and 4 turn buckles 2nd picture, The angle alum. for the turn buckles is 2x2 x1/8"
The table was design to be raised and lowered, BUT for how I wanted to use mine I saw no need to raise the table.
The table is nice and flat and square to the sanding belt.