Propane tank placement

For permanently mounted tanks, they must per DOT regulations basically be within the "cage" of the framework of the vehicle: not hanging underneath the bottom frame, nor above the roof, not in front of the front frame or behind the back frame. I don't know whether or not this theoretically applies to portable/removable 20# tanks and similar, but nevertheless it is very good advice.

What about the built-in tank is bad? If it's just the fittings and valves and such, a local LP gas distributor/dealer (the kind of place with trucks that go out to supply people's homes for cooking etc.) could probably put in replacements and get it working properly without too much cost or difficulty. If the tank itself is rusted or leaky, that's a different matter, but also a comparatively uncommon situation.

I have seen rear mounted Propane tanks, Epically on Truck campers.

however most TTs and 5ers the rear bumper is a total joke, basically foil strong and the weight of a propane tank will very likely pretzle it a few bumps in the road away.. If rear mounted it would need to be mounted to the body and to a stud.

I would not do it.

Plus as someone said.. If you get rear ended, not a good thing,, And people LOVE to tailgate.. I checked the idiot following me the other day (Wed or Thu forget which) at leass than 1 second behing my door post (I was in a car) proper distance is the time it takes me to travel 3 Seconds Or more) and that's from the Rear bumper So he was like 1/4 the proper distance.. had I stopped fast he'd have been in 1: My back seat and 2: a very uncomfortable position in court.

Just as long as you don't rear ended. Then you may regret it.

I see nothing wrong with it as long as you make secure holder for it.