When is to much Plants ?

I think your biggest worry is going to be humidity (bud rot, fungus as a result)... if you can keep the airflow going and the humidity down to acceptable levels, you'll have a chance... being that they're sativas will give you a definite advantage in this area... I would NOT try it with indica! Good luck...

i'd def keep leaves maintained one way or another.. avoid overlaps creating standing water on leaf surfaces etc... get a dehum if you don't have one... they'll produce a lot of vapor while transpiring.

make some crawlspaces so you can get in there and do maintenance if it can't move easily. the danger is excess humidity and an environment that creates opportunities for microbes to flourish. keep that in check and it isn't too much.