lol I am always late but if you see your males tail under the females tail then you are good to go for the sexes. I have been told (and have observed myself) that the boys like to be on the bottom How old is your boy? If he is younger than expect shorter locks, if he is older and bigger he can lock for what seems like forever! My pastel would only lock for about an hour when he was small (500g) now that he has hit 800g he has been locking like there is no tomorrow and staying locked.
Good luck and hope to hear all went well. Oh and don't be upset if you don't see them locking, some are shy.