Susan & Rick,
A couple other posts have mentioned the ductwork. You don't mention what layout you have, but I know that in mine (rear bath, mid twins) as Andy said, the ductwork tends to leak a lot of air along its path to the rear bath.
I discovered some holes in the metal ductwork, round, about 3" in diameter (at least two I have come across) that were created either at the factory, and have been left open by the OP, I'm guessing. On one (under the curbside bed) the disc that was removed was just loosely sitting on the ductwork partially covering the hole. The one under the galley sink was taped shut.
Also, the joints in the ductwork were originally taped with some kind of tape that looks like paper. Of course, in time, these paper patches on the joints loosened, and now leak like crazy.
Finally, when I removed the trim rail and wood skirt in the front of the bath tub, I found that the ductwork connection there was again (and I would say intentionally) left loose and leaky, with another opening cut into the top of the duct just where the duct joins the register .
The only result of all this that I didn't appreciate was that the bathroom was always cold, since very little air actually made it out the register.
I felt that the factory's original intention was to allow the places beneath the kitchen cabinet, my (curbside) bed, and the bath tub to have some heat.
My objective was to warm up the bathroom a bit. So, I cut a piece of metal to block the cutout in the ductwork near the bath tub register, and wrap the register's tail (that fits into the duct) in thin foam to block most of the air leak under the tub.
Just this made a big
difference in the bathroom comfort.
I wanted to keep the spaces under my bed and also under the sink warm, and so I stopped there.
To cut to the chase: I would add adjusting your ductwork's outlets, both visible and hidden, to your job list to warm up your coach.
You could easily direct more heat into places you want it, with possibly dramatic improvements to your situation.
Get a roll of tape and maybe warm up!