I am having to replace approximately a 3' by 2' area of the cabin overhead (not the outer shell - just the laminate makeup of the underside of the cabin shell) of my O'Day 19. The overhead consists of the fiberglass surface then the laminated balsa core THEN a hard green foam of some kind before you actually reach the cabin shell. Because of water damage I must remove a good portion of this "hard green foam". First, what kind of foam is this material? I talked to Rudy at D&R Marine and he was unaware of this foam (which surprised me!) Second, do I need to replace this foam with identical material or can I use something else? If I need to replace it with identical foam where can I get it? Thanks in advance.