Interior trim? What to use?

Google... ceiling/sidewall batten or search words close to it.

http://www.all-rite.com/paneling/ct140-white-rigid-ceiling-trim

side view shot of something close to above pic

http://www.all-rite.com/paneling/p95-white-rigid-divider

Thanks for the ideas all. I got some good ideas. The fabric idea even made me think of some type of fabric rope! Something that looks nice and can just be glued to the ceiling and not the wall so there is room to move as you drive. Might look nice... also may look TERRIBLE! :)

I was familiar with the PVC stuff but the Home Depot near me stopped carrying it. I just ordered a nail gun and I will just try to FORCE the wood along the ceiling. I was trying to glue it with some fast set glue, but it was not strong enough.

But you all saved me a TON of time looking anyway. Thank you!

RV seem tape. Getting right color is hard part.

http://www.all-rite.com/seam-tape

http://affordablervparts.com/product/1-roll-self-stick-adhesive-wallpaper-seam-tape-rv-roll-lakeside-cherry/

Spend the bucks and get heavy duty roller. Not cheap but worth it in long run.

The thin trim that is used in rv's and mobile homes is available at mobile home supply places. It is usually covered with wallpaper type vinyl. If it doesn't match you could paint it before installing.

If the curves are gradual, quarter round may be flexible enough to be suitable. There are also some PVC trim products (including some with woodgrain appliques that very closely match the honey oak veneer or applique of my RV's cabinetry) that are incidentally more flexy than actual wood.

If you want lighting, maybe a series of some of these with the corresponding LED strips would be the ticket.

You might be able to do some sort of upholstery around a core of some sort (a strip of luan would probably suffice) held on with e.g. screws and snap buttons or something like that. With a little bit of padding, it could follow the contours where things aren't precisely straight and flat.

You may have to use your imagination and just do some wandering around at some Home Improvement stores to see what's available. I've done a LOT of home remodeling over my 62 years of life and have found that conventional, normal, cookie-box cutter items rarely works with something that already exists. Almost every time I stumbled into a problem like this, I find myself wandering around the store in some section completely unrelated to the item I'm actually needing, and then .... BINGO! And idea is born.

My wife wanted a hat stand and wanted me to either buy one or make one. After searching the easy way (buying one), I drew a blank. I found myself one day in the curtain rod section and then it hit me! One of those curtain rods with the rounded ends, cut in half (to make 2 posts), stud in a block of 2X6X6 with a hole in the middle to support it, sanded, stained, varnished, and detailed, and BINGO! She had a hat rack she could put on her desk!

So, if you look around, you might find some kind of molding that might work far better than anything solid wood. Maybe a garden hose with lost of flexibility, painted, and attached for a small, really unique crown molding look. Maybe black electrical tape to emulate crown molding. Maybe a rubber seal that would be used around a door frame? The sky is the limit, only limited by your immigration and construction skills.

I'd look for some L shaped rubber seals that goes around windows or doors and then tack it on with some finishing nails and Liquid Nails. Something like that.