Brad, really the only way to confirm the sex of your snakes is to have someone probe or pop them for you. An exotics vet can probe them for you for a nominal fee, or try to find a herp society near you and see if there's a member who would be willing to sex them for you.

Since you're not sure which are the females, I'd definitely make sure none of them are under 1500 gram, a small female is going to have a harder time with being gravid and laying eggs.

Generally, when the pair are locked up, the male's tail will be on the bottom and the female's on top.