I know I saw a thread on one of these made for RVs so it didn't need a 4" wall. Seems like a great idea to supplement the furnace.
Found it; it is called the Platinum Cat and comes in two sizes. A member named Sleepy installed in his truck camper and has a thread on it.
And, okay, I see it was mentioned at the top of the page. Shouldn't be hard to get as they sell direct to the public. Oops, 8 week delay. Arnie will build custom units as well if the regular model doesn't have connections in the right spot for your application.
