I know O. vulgaris are kept in LARGE tanks together without (much) issue as long as they are about the same size. The tanks I have seen (photos) house between 5 and 10 with very limited sheltering and only the small animals end up attacked. If you are not seeing aggression (quite obvious in some species) I would (holding my breath) continue as you are doing.
I ended up with a boy named Sue (SueNami) because the missing arm was the hectocotylus. I suspect he courted a female that wanted nothing to do with his amorous attempts. The only caveat is that this species (O. briareus) is quite cannibalistic. I was able to mate a pair of these (hatchlings but no survivors after less than a week). Neither animal hurt the other after two pairings but they were siblings and had seen each other across the room all their lives. I am not sure the familiarity was helpful but think it may have been.
I ended up with a boy named Sue (SueNami) because the missing arm was the hectocotylus. I suspect he courted a female that wanted nothing to do with his amorous attempts. The only caveat is that this species (O. briareus) is quite cannibalistic. I was able to mate a pair of these (hatchlings but no survivors after less than a week). Neither animal hurt the other after two pairings but they were siblings and had seen each other across the room all their lives. I am not sure the familiarity was helpful but think it may have been.