Well, the redneck school of engineering recomends that you make a quick
prototype out of poster board/foam board/sheet metal/whatever. Then mount the
sucker in the back of a pickup truck, as it would hang normally, making sure
that its in the free-air stream.

To test, start driving and watch the rear-view mirror. That should answer most
of your questions real quick.

Just a thought,
Harry "10 tie-downs ain't enough" Frey
Wright Brothers Enterprises
Wright 1902 glider, 1899 kite, 1878 Bat