Catalytics work great but they have a big drawback - water. I have one in my 20' camper. If kept running for long periods of time, you'll have water running down the windows. On a hunt a few years ago, it was so cold that we had to keep it running during the day to keep the water from freezing. After 3 or 4 days of steady burning, our matches were too damp to strike and we had ice on the insides of all the windows. All of our clothes and bedding felt damp, too.
Did you have any windows cracked?
Yup. It can still happen, but an open window will greatly reduce it. Learned that lesson the hard way myself.
Personally, I wouldn't mount any heater to the wall. Fire chances are too great.
I'll run my fridge while driving (still not recommended by manufacturer) but that's it. And only the fridge runs when I'm not in it. Seen the aftermath of guys wanting to keep their rig warm while away.
I basically deal with a cold trailer. Water bottles in a cooler without ice will prevent freezing (inside the trailer) if it was at room temp when you left it. To quickly heat a trailer when I return, I turn on the heater and a couple stove burners for several minutes. That seems to do it. Usually want to heat up dinner or coffee anyway.
Coldest I hunt in is low teens though. Lower than that, I don't know if my solution works. You can always fill the empty space of the cooler with towels. That helps
