S2 8.5/8.6 is not the same hatch. 8.5/8.6 has a trapezoid shape. Hard to measure due to the rounded corners. But it looks to be 22" wide at the front edge; 28" wide at rear edge (mast/hinge end) and 21" in length (front to rear). Corners are 2" radius, although the front looks a bit bigger than the rear, but I believe it's the illusion of one corner (rear) being less than 90 degrees, and the other being obtuse (front). It is flat. Battens are 17 7/8" by 5/8". OOPS, I didn't measure the thickness, but about 1/4".
(unlike the companionway hatch cover which has a curvature to it, which is 30" wide by 28 1/4" long (front to trear), rectangular, but about a 15/16" rise at the center.) Square corners, but front edge has a bevel to it to match the angle of the companionway.
All are 3/4" thick.
Good luck. Let us know what yu ahve in mind.
Bron
S2 8.5 #088
Rocky River, OH