actually what was successful was a test. i researched the various 3M spray adhesives and chose 3M 77 spray adhesive (maroon can).
I used one panel, and followed the directions on the can to spray on the headliner material, let it cure for about a minute (still tacky but the adhesive doesn’t adhere to your finger–it just feels tacky). the directions also refer to two-surface bonding, but I went with just a single surface.
I used the underside of the galley hatch as a test bed. I had applied one coat of epoxy to it, but it’s not sanded so it’s a bit rough, similar to what the inside of the cabin will be (I don’t plan to do much sanding before I give the interior a single coat of epoxy).
I then inverted the hatch cover on a pair of sawhorses and left it to sit overnight.
this morning, the panel was still firmly attached. I could remove it without destruction (save for two spots the size of a pencil eraser that stayed behind on the hatch cover).
if I were to reattach it, I probably would give another light coating of spray.
when I do this for real, I plan to cover about 50% of the surface of each headliner panel (the edges and some random places in the center). based on the strength of the test piece, 50% coverage should be sufficient.
if one were to sand the interior smooth before epoxying, I would imagine even less spray adhesive would be required due to better adhesion to a totally smooth surface.
when I run my wiring I will make sure to route the wires where they will land in the center of the panels rather than the edges.