Biggest I've seen pics of was the one offered up for sale out in Vegas that shredded a Dovii. I think it was 26-28 inches. Sole propriotor of a 700 gallon.
Mike H20 has one between 20 and 24"
Angeladay had a pair of monsters back a few years ago. 24-26in and like 18-20 in.
"Hannable" My old shoal destroyer was 16in when it went out to Chicago to JimmyV then MFSwets. Not sure where it's at now but I think it's prolly over 20.
There's another guy from the "other" site that actually had 3 over 20" if I remember correctly. Which to the best of my knowledge pre-dates all the above.
Sorry I don't have pics but I'm sure some searches would yield pics.
I'd post a pic of mine but at 7 inches it's laughable compared to some of the truly impressive awe inspiring specimens listed above.