I guess no one knows? Sometimes I feel like I'm the only person in the world trying to grow as much food as I can in a limited space. I can't ever seem to find specific information to help me make the best of my situation. Really frustrating.

maybe this link would be helpful
http://forums2.gardenweb.com/forums/balcony/

"What if though, you wanted to grow as much fruit as possible, what would the ideal size (in a container) be?"

The larger the container, the larger the potential fruit production. So...choose the largest container that's practical for you.

I also go for max production with fruit trees and vegetables. Fruit trees each have their own requirements depending on the type and rootstock. For example, a dwarf mandarin tree can put out a lot more fruit per sqft than a full size tree kept in a small pot.

Also, I grow everything in fabric Root Pouch containers, which helps deal with expanding roots. No matter what, the roots will outgrow your container and effect the health and productivity of the tree. You can't treat fruit trees in pots like they're full size trees in the ground.

What you need to do is research each tree you're growing. Citrus has different requirements than avocados. There are no dwarf avocados but there highly productive fig trees that can be kept small.

I keep most of my trees in 15 gal pots. Smaller veggies are in 3, 5 or 7 gal pots depending on their needs.

Also, you're far from the only person interested in max food production. I'm building an aquaponic setup designed for veggies. Vertical systems also max out sqft space. Google outdoor or balcony hydroponic systems and search images to see all the crazy contraptions people build.

Overall, there's far more to growing productive trees than pot size.