I think 5 in 5 gallon containers would be a good number of plants in a 3x3’ tent. You could be daring and go for 9 but it would require some heavy pruning to make it all work and not sure if you want to put that much into it. 5 healthy medium sized plants and some very minor training will give you a nice canopy of colas and much easier to manage. If you do decide to grow more I would suggest smaller containers and go for more of a SOG type grow with 1-2 gallon bags/pots to keep the plants from getting too big and to be able to fit more in your tent.
