Well...like any experimenter out there...you just gotta try things out...
Extended the diffuser out another 17" from where it was. It's about flush with the back edge of the aero cap and the tailgate when it's down.
I doubled up on the horizontal part so it would have some support besides the screws and Gorilla tape holding it on. I curved it up using my variable heat gun and one of the roof rails on my camper top. Not sure on the angle...but I'm not worried about that fer now.
This kinda simulates one of those hitch racks but this one won't hold anything...
Piccies!!