Ah, I have one. Didn't know what I was getting into when I pulled a bunch of 1/4 inch fry out of a warm ditch. I have read that exceptional individuals get to 10" and the record is around 12". So yours is in the range of decent size for them.
Mine is the biggest fish in his tank, and hides most of the time now. It's been an interesting fish over it's lifetime, but I wouldn't want one again unless I had a bigger tank.