> while we are talking bulkheads, I am considering using rigid foam ( 5/8
> foam core ) for a rear bulkhead coated with epoxy to seal it. that would
> provide deck support but not the wieght of plywood. although I might end
> up with a sandwich of doorskin to avoid all that white in an otherwise
> wood appearing boat.

> any reason to not use foam core for bulkheads ?

use on or the other not both, the water that will eventually trap between the plywood and the foam would eventually rot the boat.