When I transfer everything over from my father in law's tank, I inherited an army of clowns. He loved them, and despite my advising against it, he insisted that they would be fine. I have a pair of large tomates, and four perculas (yes, 6 clowns in a four foot tank).
I would strongly advise against multiple pairs of clowns.
There is a pair of perculas that generally tolerate one of the other clowns, but the 4th percula is the odd man out so to speak. It takes shelter up in one far corner behind a powerhead.
The tomatoes rule the tank, without a doubt. They are generally a major PITA. They harass the perculas, and the sixline, and are constantly digging, and spitting sand all over the tank.
Some days the perculas are fine, but other days, the 3 perculas are constantly going after the 4th. At some point the 4th is going to be removed (if I can get it out), or it'll likely end up carpet (or hardwood as it were) surfing.