Google Fiber is used by several people with USG-XGs, there's nothing incompatible about it. You can post on community.ubnt.com for help, and can tag me there (UBNT-cmb).
You're reselling beta hardware, which you expressly agreed not to do when you purchased it. Plus doing it at a major profit, which is even less cool. I'll give you a chance to take this down, but if it isn't you'll be blocked from beta offers.