Headlinings are quite easy to install. I would not put in the automotive type with fabric from one end to the other. Epoxy in strips of plywood from side to side about every 18" and small panels covered with whatever you choose for looks. I am using laminate covered 1/8" ply. The panel seams are covered by hardwood attached with screws. This allows for removal of only a small section for accessing deck hardware or wiring. You can insulate as well with 1/2" closed cell foam easily. Here's a link to an interior redo of a Nicholson 31 from Atom's site and a pic from the same site below.
Atom Voyages | Nicholson 31 Refit