@Happy Warrior: Thanks for adding your perspective. The site I linked to was from the University of Washington, so I suspected that "you guys" had a broader distribution, but I confess to not knowing what it is. I know that it isn't common on the East Coast or in the south.
I may not have been clear on what I think about the constructions. As to the possessive, I am primarily a descriptivist. I would not consider any form of you guys a misuse of language, though others do. It's logical grammatically for people to have a possessive form of "you guys." From a linguistic standpoint "your guys's" and "you guys's" are both fine in colloquial speech.
I advise against language learners copying them, however, unless they live in an area where people talk that way and they can manage to use the forms correctly and appropriately. That is, you might use it when you were at the bowling alley with your friends, but you probably shouldn't use it in a business meeting. And if you use "you guys" around people from the East or the South, they may ridicule you or accuse you of being sexist.
I use "you guys" all the time, and there is nothing wrong with it where I live. I probably have, on occasion, said the possessive form, but in writing I would always rephrase the sentence.