AFAIK and I've not checked lately, it has not been known how to sex RTC from external features. IDK about the hybrid but since the same holds for TSN, I'd guess it is not known either. The hybrid is supposedly sterile anyway, so normally who cares about its sex, except the females may and probably should grow bigger.
For larger RTC like over 2 feet, I have a supposition that females are bigger growing, girthier (the usual characteristic), and have flat and straight (in profile) heads while males' heads are a bit rounded.