I think that an under-the-van propex install could work, but see at least a
few downsides like:

-larger holes cut in the van for passing the air circulation (intake and
heated air outlet) pipes through vs. the smaller burner intake and exhaust
lines.
-More difficult installation since a protective/sealed enclosure should be
built to protect the heater from the elements.
-Possible ground clearance issues with the intake/exhaust pipes for the
burner that stick out of the bottom of the heater.  Modifications to the
propex may reduce the vertical space needed, or mounting location may
eliminate this issue, etc..

A few nice benefits would be less space used, and I would expect a more
quiet operation.

The propex seems designed to mount inside though and you'll have to work
against that.

I installed mine under the rear seat on the passenger side of the van with a
sturdy enclosure over it so that while I lose volume I can store items on
top of, and around the heater without worrying about damaging it etc.

So far in Westy's I've seen Propex heaters installed:

-under the rear seat in different locations,
-below and in front of the water tank in the "secret" space there, this is
inside the small cabinet to the rear of the fridge essentially.
-under the drivers seat,
-on the floor behind the passengers seat
-and I think I recall one being installed in the bottom of the hanging
closet?

I guess the different locations indicate that there is no clearly best
install location at this point.  Of course it could just be the
individuality of our community members coming out in yet another way.

Send photos if you install the Propex under the van, I wouldn't mind
reclaiming the space in my van if a better alternative comes along.

Jonathan Poole
'83 AC Westy, that tries to dodge weather that requires the propex

"Does anyone mount the propex under their vanagon rather than inside
somewhere?

Space in the rig is at a premium.  I'm thinking that it could be done.

Any thoughts on this?"