Simon sez:
<<However, if one makes the window at the rear door or hatch openable (as
suggested with a safari rear window), one would be courting disaster.� Air
contaminated by the vehicle's exhaust would be sucked in.� The occupants
would soon develop headaches, fall asleep and die from carbon monoxide
poisoning if they didn't first get wrapped around a tree when the driver
dozed off.>>

I could not agree more.  I have carried long boards (16' or 5m) with the back 
hatch open, and it is foul!  The exhaust flows right up to the front.  I had 
all windows open to try to get some fresh air.  Luckily I only had to drive a 
few minutes, but I bet I lost some brain cells in the process.
       I can't imagine anyone driving around with one of those rear-hatch 
props in place -- that would be truly nasty.  And if you did live through it, 
the residual smell in your upholstery would be horrible.

Bill Marshall
85 GL Tiico
Bradenton FL