Steve,
Hope you and Marty are having a good Holiday season! I remember when you were at Alumapalooza, you were having the same problem that I was with the gas shutting off to your grill when you connect it to a large LP tank with an extension hose. I found a solution that works for me that you might want to try. I changed the end of the hose that connects to the cylinder valve with one that screws into the valve in place of the ACME connection which screws onto the outside threads of the valve. Since I made this change, I have not had any problems running my grill from the large tank. I think you can also buy the extension hose with this fitting already installed from the same manufacturer that made the other hose but I took the cheaper route and just changed the fitting. Hope this information helps and see you on the road!

Happy Holidays and Safe Travels,
Tim