That is a great deal on a very nice trailer!
Julia at GEBE told me that many of their users have BOB trailers, but I had problems mounting mine (I have the standard BOB trailer, not the IBEX, so perhaps you'll have better results). I'd bought the heavy-duty rear wheel from GEBE, which uses a solid axle. That meant I had to use the "Bob Nutz" to create attachment points for the the trailer, but the points were too far apart for the trailer hitch to fit. I was short on time and didn't want to fuss with it so I just went with a front rack. That worked fine, but it would have been nice to use the trailer. I hope your's works for you; it's a great trailer!
I enjoyed your "Gebe" build thread. Looks like you've put a lot of thought into doing it right! Well done!