Indeed this is an excellent build, and is probably the strongest looking cap I've seen.
If you do a Gen2, you'll probably want to consider going at about an 8° angle, this would raise the back 6 to 8 inches off the top of the tailgate. It has shown this will have a good combination of Cd reduction and also reduce the lift coefficient considerably which will make your truck feel much more planted at highway speeds. Additionally you'd gain some under cap volume.
It is a common misconception that you want the back as small as possible, and while quite good, it is not ideal. You're probably getting 70% of the benefit of a very well designed cap.
Sorry to nitpick, you have done a great job. I just want this here as a guide for anyone else who looks in on this and it will help them design a better cap.
Thanks for sharing!
What did you use for a cover? Is that coroplast?
Here's a pic of my angle analysis. The wing shape is the Ideal Template overlayed on the truck. If you don't curve the top, it's best to go with less angle to compensate. The line is at 8°.
And here's a link to a
Bigger Version of the illustration.