Lets see...
I have got 1 large Pacus (about 12"), 1 convict, 1 red jewled chiclid, and 3 fighting gourami (pink ones), all at full size except the pacu. Obviously 1 Red Tiger Oscar, he is 4-6" right now, just a baby.
The jewled, and the convict were at full size when I put the oscar in, not too long ago.
They all get along good. The convict and the oscar, I think are in love.