I have the Marshall Brass Extend-A=Stay and have moved it to my second motor home. One of the things I like about the Marshall Brass unit is that it has check valves in the connections so you can disconnect the external tank and open the valve to the main tank and there will be no leaking through the hose going to the external tank.
I added a brace to help support the regulator after installing the Extend-A-Stay. The added extension with the installation of the Extend-A-Stay may lead to excessive vibration at the connections to the main tank. When I installed my first one, the connection at the tank vibrated loose while traveling on a rough road and caused a leak. After attaching a bracket to support the regulator I've had no problems but I do check the connections frequently while traveling just to be sure.
Pete - Full Timing
2000 Country Coach Magna 40', CAT C10, #5892
2006 Jeep Liberty