You will probably have to wait another 6 months or so to sex your Rhino. Femoral pores are not a reliable indicator for this species but by the time they are about 18 months old you should start seeing hemipenal bulges if it's a male. By 2 years of age if you don't see them you can be pretty confident that you have a female. Can you take a photo of the hind half of the animal from the side with the tail being lifted up and curved over the back? Bulges are easiest to see from the side with the tail lifted.