I think ggray has the right approach if you want a hard surface. However for a
headliner you need to find some sort of rubber material -- a hard material applied with a texture roller could result in scuffed and scraped scalps for the crew when conditions are rough.
If you're looking for a high finish level you could build a
headliner made of a variety of materials. Plastic or thin wood
panels held to furring strips, or you can buy foam-backed vinyl and apply it to thin
plywood panels using 3M spray
adhesive, and put it up in sections with the covering wrapped around the edge of each section.
Another approach is to use heavy woven felt material that looks like gray burlap, only much softer, and apply with spray
adhesive. This is used by
Corsair trimarans and the owners refer to it jokingly as "mouse fur". If you search the Farrier F-boat
forums for mousefur or "mouse fur" you will find discussions and that could lead you to a supply source.
The advantages to mouse fur or padded headliners are they will be softer if you bump your
head and they will also help deaden sound.