Well, you could just split up a pot and see how it goes. I would guess that Sansevieria trifaciata would do well. Some of the hardier varieties could do better but since all Sansevierias come from Africa that should tell you alot. If you can keep them dry, while they are cold, you may be able to stretch the zones abit.

Tell us what you have in mind, and we might be able to help.

I agree with Cena here. If you have your mind made up to plant in zone 7, keep them dry! and with the knowledge that one year you're gonna lose 'em.
Mike