Swamprooter, you might want to look at one of the US Army cot bug nets. They are made to attach to the frame of a cot, and have small loops all around it to tie off to. You could easily use it to screen that open area to keep the bugs out. I'd bring a few plastic clamps along and clamp it to your tarp. They are very light, probably not a pound, and cheap.
I'll PM you a link to one on the auction site so you can see what it's like. I like your set-up, and a bug net would make it great in warm weather.