10 TALL plants should be fine as long as your space is big enough. YOu listed horizontal dimensions, not vertical.
Usually, 1 plant per sq. ft, but depends on if you are cloning, scrog, LST, etc. If you have a 6'x6', then 10 plants should not be problem, no matter how you grow them.
Of course, I am a newbie and if someone with more experience says different................believe them!