This is something I am trying to accomplish also. There certainly isn't as much info on mobile NVIS as about other things.
I have tried screwing two hamsticks together end to end into a mobile antenna roof rack mount and tuning with an SGC-230, then bending the long hamstick over my van. This requires a strong spring.
This works at least mobile to base, it just doesn't get much WAF (Wife Acceptance Factor) and isn't very stealthy.
I have also tried wrapping an insulated roofrack with 80ft of wire. This tunes up but seems a bit deaf.
My next attempt is to do a shorted loop with a 1in copper pipe, and maybe even silver plate it for conductivity.
The best place for mobile info (that I know about) is:https://www.tactical-link.com/nvis3.htm
and the David Fielder book:http://www.qsl.net/g3cwi/nvisbook.html
For non moving use, simply connecting ~1/4 wave of wire to an antenna mount on your vehicle and throwing it over a few bushes or somehow suspending it <1/4 above ground and tuning up works well.
There are also several yahoo email groups related to this:
NVIS, hfpack, hflink.