I already try to put 6 (3 different variety) in the same soil pot, Believe it or not,it's work pretty well. however i can't tell if it could be great for yield, because the 6 clones was crappy and i decide to put them in same pot instead of garbage.
especially in soil the roots trend to stay around the pot and let the middle with low roots, with 6 roots system to fit in one pot, the roots have literally no choice to populate the middle.
To realize it like a pro, i think the answer is the genetic! some could work as hell, and other not at all.