The installation of the external supply hose was done as a permanent install due to the fact that the on board tank is difficult to get to. I would have to empty my storage compartment and then unscrew the panel to get to the propane tank valves. If you are relying on check valves that have been shown to leak to keep things safe it is unsafe in that application. Now, for those with side mounted tanks that can easily be accessed, then yes the Extend-A-Stay is fine. It is easy to turn off the on board tank, install the external hose and hook up to an external tank. When not in use the hose can easily be removed and the plug re-installed to stop any leaks.
As it was set-up on our coach it was a bomb waiting to go off.
Keith