it honestly depends on the person and how they work with the ergonomics of the gun.
I stand 6'1 and I don't find the P90 all that comfortable for extended periods of time. However I've played with a guy who is round about the same height and has no problem.
"You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here."