Some sort of tagging does sound like a good idea with more than one foxgirl.
We now have 3 hunters, 1 foxgirl, and two willing to go either way.
Ok, since I started this I'll toss out a suggestion for how to fill out the details beyond it being a fox hunt. I'm feeling a bit inspired by those links so how's this sound to everyone:
It's the present, the hunters are part of a secret group of magi (you know the ones running everything from behind the scenes) who've come together to enjoy their anual hunt. The quarry are random unfortunate women who've been kidnapped and magically transformed into foxgirls. The deal is simple, the spell expires at sunset provided you don't climax at any point. If you cum, the spell absorbs the energy and the changes become perminant. Lose and you become your captor's pet forever. Win and you get whatever you want... money, power, maybe even a place among the Magi.