Tank Cover

I talked to a friend who has 40 years experience in restoration business and advised me when I did my repair. The problem with the single piece is there is a greater chance of warping, especially in the larger deck piece. Also, there is less chance of air pockets in the glass between the wood and deck with the pieces. I planned on a single piece also but after talking to my friend and GW I took their advise and used pieces.
My friend said today that they would put the glass in the inside of the deck, then the wood pieces and put weight on this to push air out and later finish the bottom with mat and glass. Hopefully GW will get back to you and provide better guidance.
 
Air pockets can be avoided by drilling relief holes in the core before you put it down. You can see them in the second picture I posted. I bed that core in epoxy thickened w/ wood flour and as soon as I weighted things down, the goop squished up through the holes. Wipe clean prior to curing or sand flush after.
 
Grady's answer:

We use patterned cut plywood instead of a large piece because you can
imbed the smaller pieces into the laminate and work the air out better.
Using larger pieces tends to trap more air between the plywood and
laminate causing delams.

Still think I'm not rebuilding with small squares