With the sponge rubber sealing around the hatch covers, they lift up above the deck. This makes the 8 hatch cover holders angle upward. Should I add a spacer washer on the deck to square off the hatch cover holders or will the sponge flatten out over time.
i assume from your description you have a boat with what are supposed to be 'flush' hatch covers....with the four toggles that hold each one in place.
the short answer is yes. the foam/sponge rubber will flatten over time. but initially it can be a real bear to get them closed when the boat is fresh/new.
no need to add spacer washers....but you may need to give it an evening to let the sponge finally get compressed.
