Trailer wind deflector

More trailer-talk....

I have a Minden-Fab / Scheder-style trailer and tow with a 200hp V6
station wagon. The front "barndoor" of the trailer is about 1.5 to 2
feet higher than the roofline of the car. The whole setup feels draggy
on the road. 65 mph is about the limit before I feel like I am abusing
things. I get about 17 mpg with the trailer, 26mpg without. I plan on
a 3000 mile round trip this summer and with gas where it is, a few
more mpg would be nice.

I was wondering if it would be worth fitting a deflector to my luggage
rails near the back of the wagon to reduce the drag and increase my
mpg a few points (and my L/D would also go up too!).

I will can fabricate something from stainless sheetmetal that would
mount to my Thule rack. Any tips or guidelines on the form of such a
deflector are appreciated. Or is this a bad idea?

Thanks,
Adam