I used the Mr Buddy heater alot in my tent camping days and in my off-road POPUP trailer as a back-up heat source. My spot in my POPUP trailer is high on a shelf and right under a cracked open fantastic vent fan.
There is no way I would use the Mr Buddy heater is a closed up trailer. Like you I had no problem with my tents as they all have big built-in leaks with all the fabric areas involved.
The CAT HEATERS can be vented without alot of extra work. I am so fed up with my propane furnace I am just about ready to permanently install a CAT HEATER myself. Consider these photos how one guy installed one along with venting...


You certainly don't want to wake up dead one morning...
Roy Ken