When we got our Weber Q220 (a 70th birthday present) I looked into hooking up to the motor-home LP system, both on the high pressure side, still using the Weber's regulator and on the low-pressure side, using the motor-home's regulator to run the BBQ.
I was not comfortable having 20 feet or so of flex hose carrying the full cylinder pressure from the RV's tank. I found a number of posts on various news groups suggesting that the motor-home's regulator wasn't sensitive enough to handle the flow rate of the BBQ running by itself. One poster said that on the lowest setting, he couldn't get the BBQ below 600 degrees!
I decided to go with a portable propane bottle. I go a 10-pound "squatty" which has the same base ring as the normal BBQ 20-pounder. I got a Camping World "base stabilizer ring" and bolted it down to a stow-bin floor. The "squatty" fits in there really snug and I run a bungee through the handle to an eye-bolt on the forward wall of the bin.
I don't fill the bottle beyond about half full, so it's not to difficult for an old fart like me to get it in and out. I like that i'm not confined to a specific distance from the side of the motor-home to where I set up the BBQ.
Frank and Eileen
No longer RVers or FR owners