I tried this technique as well and found that it worked great for straight line taping. I had a little trouble with it on the tight curve of the body panels (2 to 3 I think) where I had to cut a few reliefs in the tape to get it to lay flat. It worked, but cutting and manipulating the wet tape was a little tricky.
I found that I could roll the dry tape, then unroll about a 2 foot section on a table covered in plastic, saturate it, then roll the wet part and unroll more dry tape into the same spot (if that makes sense). Then I only have a 2 ft area of mess on the table and the new dry part gets laid in the leftover epoxy from the last section which speeds up saturation.
Funny, I had the exact same question but I’m far enough away from the headliner that I haven’t worried about it too much. I was thinking maybe some kind of button snaps might be interesting if I could secure them on or through the headliner.
I thought about Velcro also but I don’t think the glue on most standard strips will be strong enough and will probably want to peel off on hot days in the sun.
I’m curious to see what others come up with while I continue my build. I don’t like the idea of permanently gluing that much foam to something that will need repairs, modifications, and enhancements in the future.