there is such a large neg pressure area behind the van that I doubt you could safely make any mods to eliminate it. That neg pressure area will "trap" exhaust fumes back, and will come into cabin when hatch open. I've wondered about various foils etc to be attached on the outside of van to reduce neg press area, but not come up with anything (see this extreme example on my blog http://shufti.wordpress.com/2009/11/10/vanagon-bustle/)

btw, I made my own version of the hatch prop

http://shufti.wordpress.com/2011/06/08/vanagon-heckklappen-aufsteller-rear-hatch-propped-open-gizmo/

cheers

alistair

On 2012-05-02, at 11:46 AM, Steven Shelton wrote:

> A few years ago I bought a rear hatch lock extension bar.  It came in a bag
> with text in German so I didn't know that it wasn't recommended for use
> when driving (making it of very limited usefulness if you have the rear
> screen).  With the extension bar in place while driving with the windows
> open, the air flow through the van was smooth and laminar, far superior to
> the buffeting we get normally. It made driving in in a Georgia summer
> without AC bearable.  I confess that I have occasionally used it while
> driving since discovering that it is not recommended, but exhaust gases
> sometimes leak in.  I would like to come up with a way to achieve this air
> flow without the complication of carbon monoxide poisoning.   Has anyone
> come up with a modification that did this?