The lump hasn't moved at all, but yes, it is more on one side more than the other.
I just posted in the unidentifieds folder. I looked up some pictures of M.callainos, and those looked quite similar to the one I have. I would say almost identical, but of course I'm no expert. We'll see what everybody else thinks about it.
He's still got quite the monster appetite and gets pretty active when he eats, and there's no gasping, but he's just hanging out in the back all day long, with some of his fins held close to his body (like in the 2nd and 3rd pictures...except for feeding time, then all fins are out like in the 4th picture). He's usually quite active, swimming all over the tank, so that makes me a little worried.
I finally got a shot of him from the other side, which is the side that the growth is on. You still can't see it very well in the picture; today the skin over it is a little rough looking, sort of as if it were a callus on somebody's hand that were peeling off a little.
Sorry for the extremely un-precise language, I'm not sure of what I'm describing!!
Anyway, here's the new picture. Kind of a strange angle, but he wasn't being too photo-cooperative today. You can still see the weird lump: