About 6 weeks ago, someone on this list told me I could get a barbecue tank
(propane) and a hose which would go from that tank to the inflow connection
of the existing propane tank and thus have an additional "stay longer" fuel
supply.

When I went to a propane supplier today they said that won't work because
there is a check valve which will only allow flow under the very high
pressures provided by the fill systems.  They offered a solution which
requires a valve and splitter be installed in between the shut-off valve and
the OPD valve, but that is a big job requiring the plumbing be re-done
because there is insufficient space and the copper plumbing is already
pinched as it is.

Does anyone have experience with this?  Are they correct in what they're
telling me about that simpler solution not being workable?

Thanks,
Paul in Fort Collins