Mike, let me stretch the Halon thread and extend it to the Vanagon engine
compartment.  The worst case scenario in my mind has always been something
like this.  Driving across a lonely stretch of desert in a constant stiff
wind.  Smoke appears behind, pull ove, shut down, grab the Halon filled
extinguisher and head for the back.  Now how to I apply the Halon?  If not
to hot yet I open the license plate door?  Or drop to the ground and squirt
up into the engine compartment?  And If I'm in a strong wind, will the Halon
just carry away?

The ideal setup in my mind is to create some sort of access port direct from
the outside to the engine compartment, just for sticking the nozzle of the
extinguisher into in case of an engine compartment fire.  Anyone ever though
that through and figured out how to do it?