I'm not an expert with plecos. They are sexed by the colouration in their tail fins and their vents. Males have significantly more colour in the tail and are more thicker-bodied than the females. I'm not sure how much smaller they can be and be sexed.
Very nice Gerry. One of my favourite plecos. When I was in Ontario last year they had some huge ones in Lucky's. I never believed they grew that size until I saw them in person. I love the sunshine you got there, can you post more pictures of it?