John wrote: Those Bagawest boxes were cool, but looked like they only added
to the problem...
Actually John, I can attest to the fact that the Bagawest does not add to
the problem, and have some reason to believe that they help.  Ran with
another nearly identical Westy or ten days last fall.  When we fueled he
usually took less gas than my rig, from a tenth to as much as 1/2 gallon.
In April-May of this year we ran together again, just under 3,000 miles.
This time I had a Bagawest carrier on top.  And I consistently beat him this
time, from a tenth up to half a gallon per fill up.  There are other
elements in this but I can say the Bagawest, if any effect, appears to help.