Thanks for the links!

On my little beasty - at speed the back lexan window is sucked backwards toward the tailgate. I was thinking of trying to solve that if I could. The front and rear spoilers have really settled the truck handling down at speed, but still unsure whether it's help or hurt the ET and MPH. A block-off plate in the grill helps by about 2 mph and about 1.5 tenths.

I do know that on my tonneau cover - the last bow on the cover will be forced down on every pass over 100 mph or so. I would estimate it takes roughly 25-30 lbs worth of force to do that. Of course the wind has lots of surface area to work at generating that much down force.