My current approach:
I've had 2 triple crowns in pots for 2 years. This summer, we harvested 1/2 gallon of berries from each plant for a total of 1 gallon. They are in 14 gallon rubber maid totes. I built a rectangular trellis (sort of like a box kite) about 4' tall inside the container. Because they are marginally hardy here, I bring them into an unheated workshop for the winter.

I'm considering fruitnut's approach:
For space reasons, I was thinking of going with a smaller pot and trellising them as fruitnut does in this link: http://forums2.gardenweb.com/forums/load/fruit/msg0416201220131.html. Using fruitnut's approach, each loop is centered in the pot. In my approach, there are two loops on the perimeter of the pot. So I think fruitnut's approach requires less width to accommodate the canes.

Questions regarding pot size:
1) Would the smaller pot result in less fruit?
2) Would the smaller pot result in a shorter effective life span for the plant?
3) My 14 gallon pots require frequent watering. I would expect that a smaller pot would require even more frequent watering. Would it be helpful if I buried the pot? Would either a) Some moisture from the earth wick through the drain holes or b) some of the roots reach through the drain holes for water? (These plants are marginally hardy for my zone. So I need to keep them in pots to take them in for the winter.)

Thanks.

I do think some of the roots would extend into the soil and lengthen your watering interval later in the season. But a smaller pot would probably still reduce yield and require more watering, at least in early summer.

I'm getting another Black Diamond. I think I'll try both potted and in ground in the greenhouse.

The plants are pretty easy to propagate so I'm not concerned about that aspect. It would also be pretty easy to repot after a few years.

Good luck with your berries.