I have a 150 gallon external tank on my home base site. I ran a copper line from it to a valve right beside my site and use a flexible line to hook this directly to my rig's system right "after" the onboard pressure regulator. I have a cap that I use to close the onboard regulator so it doesn't get full of "stuff" while it is out of service. When I first started using this big external tank I had the propane company check the regulator on it to make sure it was operating to spec which it was.
When I leave his site I just unhook from the external tank and hook up again to the onboard regulator and use the removed cap to cap the end of the shore flexible hose. Works well and has been since 2011 and with this size tank the propane company delivers. I have a fill up coming next week which will be my first fill since winter started. I still have 40% as of this morning, but with below 20 degree temps for the next week I will use a bit.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50X, TST Systems 507 TPMS, RV Flex Armor Roof