I have a male and a female "pair" of hoehnelii. They were kept together for several months before I got them and I was told they "did" fine. I have kept them together also (2'x4'x4') but I do not recommend it: Here are my observations:
My female seems to be dominant. She can easily drive the male off of a choice basking site with a head bob and some body rocking. I don't think either animal is stressed out, per say, but it is clear that the female rules the roost. This is opposite from other species that I have seen interact, but the same as my own household....I really feel for the little guy!
My feeling is that unless you have a very large, very well planted enclosure and lots of healthy feeder choices (mine go outside together in a large, well planted enclosure next week)., hoehnelii (like most all species) should be kept apart. Chameleons are territorial predators. They may come together at certain times of the year (like bears during a salmon run) and for breeding, but housing them together is a crap shoot at best. Just because they may not display overt signs of displeasure, doesn't mean they are not experiencing subtle forms of stress and behavioral inhibition. Experienced keepers have told me that chams are best kept so that they cannot even see each other from across a room. This makes a lot of sense to me....