Hmm, this is very interesting. I never downloaded the parts posebox (just the poserbox) so I never knew what all it had. Looks like I'm gonna' have to get it :)
I hardly ever use overlays though. I usually don't have the time to fiddle around so I check the posebox catalog for what I need and just find something that will work. hehe
That and in game anims...

But this is awesome! Really makes me think "whaaa... I wanna learn how to make overlay poses!" *throws fit* hehe and try them out myself!