It looks like you nailed the shape!! (or did you screw it?) Haha hah ha....Seriously, great work! Good on ya for not sloping the back of the cap down to right on top of the tailgate as so many are wanting to do. By leaving it up 8 inches it really improves the aerodynamics while providing more useful space under the lid.
I'm sure you're liking how it's quieter and feels more stable at highway speeds. In the winter on icy roads it really makes a huge difference. You'll have to take my word for that for a few months.
Good job for not doing so, but, if you had followed the rules of the template, you'd have dropped it quicker and been on the tailgate. By raising the back, you have improved it according to this paper here
Pick Up Truck Aero Paper. I think because the sides of the truck have no way to taper in, if you drop as quickly as the template would have you, it creates issues with too low a pressure in contact with the high coming along the side creating a vortex.