The interior of my Lancer is completely covered. "headliner", fabric, wood, etc. It looks really good. Needs a little teaking and poly but it looks good. The problem is that you can't examine thu-bolts or tangs. My rigging could be on the verge of a de-mast and I would never know it. I recommend that id you cover the cabin ceiling, leave access flaps/ports/holes to all thru-deck fittings.
If you apply liner to a sheet, consider high-end Velcro . . . OK, stop laughing. A company that I worked for manufactured spectator seating. (Mile High Stadium, Utah Jazz, Gillette Center, Joe Robi Stadium) One of our products used "hoop & latch" that had a tensile strength of 300 psi for retain panels to theater chairs without the use of screws. I'd use some on fewer 'roids but it would allow you to easily remove the panels for inspection. When I recover the panels for my back rests, that's what I'm looking into. It's a 3M product and can probably be purchased thru McMaster-Carr.