Depends on your method and plant size.

Are you flowering as soon as clones take root? or are you vegging them for a bit? Most people that flower from clone do no more than 4 plants per square foot... and that could be pushing it.

Watch this video YouTube - See More Buds at 1:13 you see a shot of 3 different SOG setups with different spacing.

You should watch the entire See More Buds volume 1. He describes in detail those 3 systems.

good luck.
Skeet.