Re: 1989 Overnighter Bulkhead - Restoration
Welcome to the site.
The original cabin bulkhead if that's what you are refering to was 3/4 in. birch plywood formica covered in a wood grain pattern. Somewhere along in time it changed. The '88 had wood grain, same grain you will find on the door to the pedestal storage boxes. Later changed to off white laminate. The cabin door was teak as I recall, later changed to starboard.
The cut pattern for a replacement comes from taking yours out - that's the pattern. If what you have was a shoemaker job, just use cardboard to make up one.
I advocate for plywood, just seal it with epoxy resin, tripple coat end grain, that''s where it rots, wickes up from the deck. Water stays trapped under it, so caulk it good at deck.
Others use 3/4 in starboard in seafoam. The original ply was actually 3/4 in., so make sure you find 3/4 ply when using ply not the reduced dimension variety found. Starboard stains and nicks easily, and expansion coefficient is not compatible with anything but itself.
I'd use 3/4 in. marine ply but it's not cheap, then apply a laminate using epoxy resin. But would use starboard on doors with soem kind of vents added.
Good luck.