Hello all: I just had a good idea last night that I put into practice. I was bulding my bench work from scrap lumber and had different thinkness plywood that I was using. I was having problems measure and trying to get the bench work frame to match the plywood thickness. so the idea was build the fram itself square, and then when putting th plywood down on the smaller thickness plywood I would lay on the frame foam rubber weather stripping, and then proceed to screw it all down, what happens is you get a nice seamless transition from different thickness plywood or whatever else you might be using. I would almost bet this will help with any kind of expansion and contraction that plywood does. Let me know what you think Reeves