Those of you who have done 50/50 split...

[Immortal_sin]

I ask the owner of then male how they want the slings shipped. If they don't mind them altogether, I do that. I have, however, packed each and every one separately too!
Depends on the species, how rare they are, etc. I usually give way more than 50%, since I don't really want to raise that many babies anymore. So even if deaths occur (which is rare), there are still plenty...I always ship extra.