Is it really controlled overcrowding with only 3 or 4 fish?
I don't think it would reduce the overall aggression or help out the less aggressive fish.
This could result in one fish getting picked on, then once that one is removed the next one in the pecking order is harrassed.
I guess my first suggestion about introducing a smaller cichlid would produce the same result.
Plus that gives less and less room for the big fish to swim around.
Anyway, I think in this case, less is more. The lesser number of fish you have, the better life they will have.
