I currently have an Extend-stay hook up on my Georgie-boy. The compartment is on the side of the coach so easy access. I have the ext valve mounted just before the regulator. So when it comes time to use an external tank (a 20lb for emergency or 100lb for predetermined long stay) I wait until the main tank is empty, then close of the main tank valve, plug in the aux tank Extend-stay hose and turn on the aux tank.
When the aux tanks empty out I swap them out with fresh ones. I fill up the main tank when I can usually when I get home. So far have never had a leakage problem. When using the main tank there is a screw in plug to close the extend-stay line.
ALK