You are correct. Its a mayan...and IME, there is no way to visually sex them. I had a spawning pair and there were no discernible difference between the sexes...and couldnt tell the difference between them unless one was laying eggs.
That kinda what I thought the only thing would lead me to believe it is a felmale ,is that my male flowerhorn chases all the male fish around the females a little less.