I'm in the same boat Geekboy. I can't even find 5/8" plywood in my area. I'd really like to add a lexan/plexi cover to my CP, so i'm toying with some other ideas. I can get 1/2" MDF and use 1/4" plexi, but i'm not too fond of that option. I could also use 1/2" MDF with the normal 1/8" plexi, but then i'll need some 5/8" t-molding. Decisions decisions.
-Kevin