Last week I got to visit the boatyard of Thain Boats, the builders of the Uganda ferry cats. They are finishing up a SIP panel houseboat with a variation on some hulls that I designed a while ago. Albert, the lead, intends to stack them in the future and stick the internals in with Plexus on the site. These are so much better than the alloy ones that the developer used to require.
Solid knitted glass laminate. No core, hence all the frames.