Hey man...its not a terrible idea, but it can become very very ugly. If the plants roots intertwine they can possibly stunt the growth and eventually kill one or both the plants. idk man, im not gonna suggest it. If u c those roots when they come out of those cups u might rethink it. lol Its just a lot going on under there to smother. BUT I have seen successful grows like this as well. So that being said, U just gotta follow ur gut on this one.