TW> bottom feed tube Large propane tank could be a problem.
 TW> And as practial matter except for very occasional
 TW> fueling one needs a Propane Pump.

hunh?? i can fill a 20lb tank from one that contains 40lbs quite easily...
in fact, i fill 100lb tanks all the time with no pump of any kind at all...
as long as there is at least 200lbs in the tank, i can get 100lbs out of
it...

or am i misunderstanding what you are saying? surely i can connect a 300gal
propane tank (quite larger than a 100lb tank) to a tank on a vehicle and
fill it just like filling a 20lb tank for a gas grill...

)\/(ark