I took two sheet of 3/4" ply, cut 4" off one side (Ply is now 96 x 44) and cut the radius on both. to look like this.
Cut out the center, i did a 5" rail:
Then the second piece of plyyou cut 1.5" all around OFF (you will use this piece so leave it one piece). The center of this is your playing surface.
I then put the rail and the outer ring (under rail) together. Then with the rail on the playing surface I drilled counter bors for the T-nuts and then drilled thru holes for bolts.
Then you can screw your legs to the underside, or add the a piece of ply were you plan on mounting your legs, the it is ready to upholster..
1" thick padding for the rail - 55ilb or heavier. Try to get one piece that will cover the entire rail with no seems.
1/4" closed cell for the playing surface. Try to get one piece that will cover the entire playing surface with no seems.
Vinyl: https://www.amazon.com/gp/product/B0042TOBM8/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 Good stuff.
Try and get the foam/padding locally, it will be cheaper. I spent about $83 on amazon with like $15 shipping.