Don't forget that LPG is heavier than air so don't cover the lowest vent opening all the way. Your RV will have a leak detector at or near the floor if for some reason it should leak to the interior. Check and test frequently. Another issue with 12v is if you do forget to turn it off you better hope you have a battery isolator or the charge wire is hooked up correctly so that it will not draw off of the tow vehicle when the key is turned off. Not only that, draining batteries till they go dead ruin them. Also consider the length of the charge wire, the gauge and even if your altinator can keep up with the demand. One more consideration. The 25 to 35 gallons of fuel you carry underneath your tow rig, in a plastic tank mind you, has way more "explosive" potential than a steel LPG tank. LPG tanks just don't explode as easy as you might think.
The valve is also designed to "pop off" before any pressures build to the point of a tank fail and that takes exposing it to very high temperatures. I understand trapping gas in a compartment would be of concern but there is already going to be plenty of air circulation. If you look at the very bottom of the gas compartment, is the bottom seal missing or cut out? Check and see. It most likely is for the very reason the gas is heavier and the manufacturer does not want the gas to pool on the bottom.
Start here and read this, educate yourself and read the other subjects.
