Oh...you can fill in the open vent holes in a number of ways; we found an old, fiberglass, one-piece bathroom pulled from an RV on CraigsList for free and cut it up for patches, then fiberglassed them in using blue masking tape to hold them in place while we worked around the tape, then took the tape off and finished the job. Lots of careful prep, care while working, plenty of sanding, wiping down with acetone, fairing with Bondo-Hair, more sanding, and finally washing with dish soap, letting dry, more acetone wipe, and priming with Rustoleum Wood and Fiberglass Marine enamel primer (white). You can use Kilz, too, according to many on FGRV.
Paul had to fill 59 holes in ours, the smallest very tiny, Bondo-Hair "fairing" only needed, to the 2 x 3 foot fridge vent hole. He's gotten really comfortable with fiberglass, but six months ago he was afraid of it. (See the Fear of Fiberglassing
thread on FGRV.)
I'd use enamel paint
, though it usually takes a "while" to "fume off." Give it some ventilation before you seal yourself in with it. I don't use enamel in our house, except on woodwork, but this is going to take a jostling -- as they say, a trailer endures a "rolling earthquake" every time you tow it.
Would you let us know how you're doing with it?
We love pictures...not that I seem to be posting any.