I think all that air gets under the front, so that any side vector can do your
steering for you.  I've experienced a similar effect, less pronounced, when
a bus or Vanagon is loaded heavily in back.  I now figure the back of the van
is doing its share just carrying the engine, so I try to load the heavy stuff
immediately behind the front seats.

Has anyone lowered a Vanagon?  I look at the coil-spring brackets that JC 
Whitney has to as-if take one turn out of your coil springs, and I ponder.
B.