Who said it's too early? Mine are locking up like crazy. (what I am waiting for is results of those locks).

What I do is wait till I observe the female attempting to "cool" herself by wrapping around her water bowl, or by staying at the cool end of the rack. Her first shed after she starts wrapping, she gets paired with a male (if she's on my breeding schedule).

I have sometimes had to put males that were "first timers" or slow starters with an "established" female first to get them started and it has worked for me.