This project has probably expanded from what you originally thought, with all the factors people have suggested, BackPackHiker. I hope you'll have the time and energy to do all this testing, because there have been a lot of good ideas offered. I thought of sending you BER's Cloud
bridge to test, as well, but decided against it, because it's not commercially available to others, and besides, BER improved on it with his version 3, and there may be a version 4 by now. In that same vein, Angry Sparrow has a Griz Bridge that he has shared with quite a few people. We had the opportunity to compare it with the Cloud Bridge at the Mt. Rogers Hang a couple of years ago. Again, it's a DIY hammock, and I think you do well to limit your tests to models that can be purchased by more people.
Now, having simplified your task, I'm going to complicate it. I think you should enlist a panel of testers - as many as possible - to offer their opinions on the comfort of these hammocks. Further, you should try to arrange for each tester to spend a night in each hammock. Of course, the test group should include people of all shapes and sizes - maybe some with experience with bridge hammocks and some newbies, too. I know that's a tall order. My $.02. Good luck.