Extend-a-stay or Stay-a-while "plumbing".
I have an older Class B with a long, narrow propane tank under the passenger's side. The valve from which the hose leaves for the regulator points forward.
It then curls up and back, running to the regulator, which is mounted under a shielding toward the rear of the van. That hose then curls around again and enters the regulator pointed forward. This is about a 3 foot run.
(I doubt this is making any sense. Wish I could draw it.)
If I mount my new fitting on the valve coming out of the onboard tank, I push my hose forward, making it too short to run back to the regulator. It looks as if I would have to buy a 5' hose to make it to the regulator.
And I'd have to buy a 15' hose to make it to the auxiliary tank on the rear cargo carrier. I'd have to "hide" about 30" of that.
Now. If I can mount the Extend-a-stay or whatever at the regulator, I should be able to use the same hose as comes from the valve at the tank, and use a 12' hose to run to the auxiliary tank
All of that is to ask if there is any reason why the Stay-a-while with the right fittings couldn't be mounted at the regulator instead of the onboard tank. It would seem to me to be a no-brainer, and I've failed no-brainer's before.