I have done 4 in a 120g, 4x2x2 with no issues. I did however have maybe 7-8 anemones in the tank so they all had their own homes and introduced them all at the same time.
There was some fighting at first, but that cooled down as they went to their separate areas of the tank. I have read both success stories and failures when trying to keep multi pair clowns. I think it really is hit or miss to be honest.