Well, I followed everyone's advice, and moved all 14 of my Labidichromis sp. 'Hongi' into my 50 breeder, but not before completely redoing the aquascape. When I had half a dozen of these fish in a sparsely aquascaped 40 breeder, I noticed they seemed skittish, so this time I decided to go all-out with rocks, driftwood, and plants, and create tons of little nooks, crannies, and hiding places, and cut the lines of sight to make it easy for a sub-dominant male or a female to hide from one of the two dominant males.
Here are the results, which the fish seem quite happy about. They seem much more relaxed than they were before, and while this is not going to win any aquascaping contests, and certainly isn't typical of the biotope they come from, they seem to be happy, which is what counts the most.
Sorry for the crappy iPhone pics.
The obligatory full-tank shot:
This tank had a Matten filter setup as a tank divider, but I moved the filter sponge all the way to the right, leaving only about 2" of clear space, just enough for the heater and the uplift tubes: