Run a piece of plexiglass the full width of your body from the tip of the hood to the top of the windshield. Add some sides to divert air there and you should, aerodynamically speaking, be better off. You might look a little funny tho...

Like the others said there really is no solution when driving something similar in aero properties to a sheet of plywood

 

I like my plywood aerodynamics of my jeep . Makes other cars seem gawdy Like a spoiler on a back of a truck.