Well...it's not set in stone fer the angle. The scrap steel stud was handy fer me to prop up the end at the time just to git an idea. What yer seeing mostly is the droop in the coroplast as it gits away from the steel stud.
The height between the top of the tailgate to the coroplast is about 11" and the height from the bed to the top of the cab is about 21". The distance from the bed to the end of the tailgate is about 78". With the mockup as it is now...I can see pretty good out the back.
Keep in mind that the rake of my truck is rather...um...severe when compared to other trucks. I'll have to measure the rake angle at some time to give you an idea of what it is. You can see it in the "grid" piccie above (post #5).
The current ducktail is duct-taped on fer the moment. I'm thinking about putting down some 3M foam tape or Gorilla gluing a metal strip with some threaded studs facing up to fasten it on with. Not exactly sure what's gonna work though...
I'm still building up my half tonneau first and see how well that works out. I really like seeing out the back window a lot compared to when I had the camper top on with the tinted windows.