Replacing all bulkheads on my Cal 20. The original build seems to be half inch or 3/8 plywood tabbed directly to the hull. I don't see any spaces or foam. I don't see any hard spots on the hull either though. Is there a way to do a decent job of it without using foam? If not, what foam do I use? I have done a fair amount of searching and YouTube watching and it seems like most people just set the new bulkheads into a thickened epoxy mixture and then tab them in.