Mr Shepperd.., GREAT action of yours! Getting your aerodynamic improvements into actuality and getting them to be of use.
I had my trucks, the last one:
2000 F. Century raised flat top,
500 Cummings red top,
10sp over w/22.5's(NO cheena made tires!),
and running spread flatbed and usually 75,000 lbs.
Made average of 8.2(~62-64MPH) +/- MPG average(per MY calculations), did very little aero MODS but anything helps!
Broke into the 10's THREE times and all were
loaded miles, other drivers listened to me like if I was telling them a science fiction story !?!?!
MORE POWER to you in this endeavor!
Keep the wind behind you and the Diesel off the highway.
Would LOVE to see ya when you come by Phoenix, let us know!