I've found that less hiding spots are better for avoiding aggression. I also like the way it gives them more open swimming space.
Instead of multiple hides, I prefer either using plants to break up their sight of the front of the tank (they think they're hiding) or if I do use hardscape, I use larger pieces of driftwood, so that it is used as a community hide, and with all the bichirs together, they seem to keep their cool.