I couldnt really say with regards to the sex I always just call it a masculine name. TBH I dont think that he is fully mature yet but I think that he is a male only because there is space for the odontodes to grow, indicating that before export they were there.
The odontodes are beginning to grow slowly but I have never been able to produce any plecs with substantial ones apart from a L104 who is hairy than a barbers floor.
It could be a dominance thing. My very hairy L104 is king of the small plecs. The tank with the 17+22cm L190 royals is dominated by a 14" gibby and my bigest L190 is yet to be introduced to them. I'll be able to see when I introduce him.
that thing is awsome! mines a tiny 4" but young and growing pretty quick, cant wait for it to get big like that, nice pics as well, mine is still a little skiddish but is getting much friendlier. How bigs your tank? any guess on age of the guy?