I bought 5 young Cubans at this year's ACA convention, all very close in size. One of them turned out to be a complete psycho, he murdered 3 of the others and a young Mayan that was already there. I saved the 4th Cuban and put that one in a 20L alone, was beat up but doing fine now. The mean Cuban only has one tank mate left, a slightly larger Mayan.
The LFS has plenty of Cubans left that are of a compareable size if I decide to replace the 3 that were killed. But I don't think I'd put then in with the mean Cuban, probably the other one after I figure out were to move the fish around.