Lovinlivin,
Sorry you didn't get a response yet but I didn't see your post until it was brought to my attention. I'm sure others didn't either. We're usually pretty good at responding here.
I've got a lot of experience with cage culture and Bill Cody is even more of an expert. I look for him to come along shortly. Anyway most of the literature says you can go up to 15 lbs. per cubic foot for bluegill that size but I never go above 3 lbs. per cubic foot myself. Perhaps the higher end is with the addition of aeration?
Also you should be fine with 1/2 inch mesh for 3 to 5 inch bluegills. Others species that are not as wide would be a problem though.
A link to a Powerpoint I recently did on cage culture for an aquaculture conference:
http://www.slideshare.net/cecilbaird1/2-cage-culture