Every time I see those red solo cups, this song pops in my head now.
Not even a country fan but...
[video=youtube;BKZqGJONH68]http://www.youtube.com/watch?v=BKZqGJONH68[/video]
As far as transferring, most wait until sex.
I'm tempted to try to cutting out the bottom, sticking them in the medium, buried about halfway.
Once they sex, let the females stay but the male cups pull out, cup & all (yes some roots will tear & they'll probably stunt but who cares - they're guys) & place the males in a double cup.
That way one doesn't need to worry about stunting or slowing down the girlies at all.
It should work just fine & maybe better than waiting until sex to transfer