Man, you guys have driven down the path I just started and have answered some questions. I have a 2007 4.8l X5, which has a 2" factory reciever installed (it has a 7 prong electrical connector - but as far as I know, only 4 wires are connected). I had it installed when I purchased the X5 to pull my small 10' cargo trailer (which has a hydrolic surge brake).
Now I just purchased a travel trailer (Coyote Lite CL232SS - 4665lbs UVW dry and is 27' hitch to bumper - brochure pic below). I also had the dealership (Calgary) tell me that they would not have anything to do with installing an after-market brake. I will head back and press them to ensure the wiring is run to the front. The RV dealer seems to have no issues installing the brake - even on a BMW. I also purchased a 750#
Blue Ox SwayPro which functions for both weight distribution and sway control. I will need it for pulling in Alberta & BC (windy on the prairies and in the mountains).
I will let you know how the wiring & brake installation goes, as well as how the sway bar works and the old gal pulls. The pics above for the wiring are very helpful. Thanks.