Drak,
First of all, I gotta tell you. I have 5000 btu in my EH (Escape Hatch), and during the day, in the sun the AC struggles to keep it cool. At night it shouldn't be an issue. But I'm going camping tonight, so I'll let you know.
I guess it's important here to note that the EH was just a prototype, and as such, it is not insulated. If I keep it, I'll be adding insulation in the roof for sure.
Secondly, I'd take another look at your side profile. Don't drop the back down so fast. It's hard on the eyes.
Mike...