I think i have someone to take on the
heater design project who is well
credentialed for the project.  Stay
tuned.  (please do not p-mail arnie
directly or we will become a burden on
him)  It might make the most sense to
submit three design proposals.  One
protable set up and two permanent, or
maybe one for the pop top, too.

Here's my criteria for a portable:

My proposal is to design a heater
specifically for the way i have been
using my Plat Cat.  Here's a photo,
along with an
explanation of the set up:
http://www.concentric.net/~Sxs/PlatCat.html

The design would include:

- 4000-4,200 BTU (my guess based on the
3000 btu 3P12)

- not too tall (3p12 height, not much
more), low center of gravity,

- designed as a "portable" with a stable
base/stand so it can be set down
anywhere, and enclosed back. tilted the
appropriate angle 10 degrees, easy to
carry (a
handle), easy to store (protective cover
for front?) and sturdy and light.

- quality quick release gas fittings for
fast, safe hook-up to a "T" in the
vehicle gas line under the sink.  (I use
high pressure gas hose, which may or may
not be "legal."  It almost has to be
able to use hose since it is a portable
or semi-portable set up.)

- a window insert made of rubberish-like
material to be inserted in the car-door
window, which is then closed on the
insert.  The flue would be inserted
through a hole in the insert, snug fit,
and the heater vent hose would slide
over the flue pipe for venting.

If there are no legal/safety  hurtles
for a semi-portable design, building the
heater iteslf will not be too much
different than the 3p12.

BENEFITS: can be placed anywhere...for
most effeicent heat delivery...or for
the most convenient location at the
moment, even outside to heat a side tent
or free standing tent (they are that
safe, BTW, no CO, temp is below point of
combustion of paper, safety shutoffs if
tipps over or malfunction).  In
addition, you only take it when you need
it.  Does not require cutting the van to
instal, only tap into gas line, attach
the thermostat to the wall and wire it
to power and the harness w/plug for the
heater.  Then, just plug it in, quick
connect the gas line, and the flue to
the insert in the window, and fire it
up.

Disadvantages: No instant flick of the
switch heat.