well, I have seen hundreds of plants flowered in 4 inch rockwool cubes.. I think there is a great explanation on how to do this with SHIT loads of pictures in one of Ed Rosenthals books.Do you really think he can keep a flowerin plant in a 2inch pot.
16 oz. plastic cup grows - Page 11 - Growing Marijuana Forum
Look at the pictures in that thread and you'll see what can be done buy good growers in a tiny 16oz cup for the entire grow.