Heres my 7" Leopard Perch-seems to eat more now than ever. Really like this fish but he doesn't like my Tigers and tends to chase them a lot (I'm reluctant to let him go though). I think he'll probably max out at the stated 8" mark.
I have one and he is indeed fairly aggressive, he is housed with some datnoids, but they are larger so they can turn the tide on him when they want to. He is a beautiful fish and he's almost full grown, so I would hold out and his temperament may change over the next year or so.
That's by far the biggest ctenopoma I've ever seen. I have 4, myself, but my largest is 4". I have mine in with dats as well...seems to be a popular choice with these guys.
I would love to have a 7"er. A LFS near me has 2 around 5" but I have not picked them up because they too would be in with my dats and I do not keep any plants in my Dat tanks. Everything I have read says to feel comfortable they need planted areas, and I wouldn't want to stress them out.