I would not use any type of core that is not specified for laminate worj with polyester or epoxy resins. Otherwise, you might find blistering, de-laminations down the road.
Carl, I was thinking of using the extruded polystyrene (usually pink or blue) that we use in construction to insulate below grade (buried against cement structure) very high resistance to water absorption, 25 psi (available 40psi). This is not as good as corecell or baltek for small boat building but for a small repair it seems very good.
I sent you a pm recently about old Lindahl hulls. Disregard. I have taken another route. Steve
