I have 2011 35d with Invisihitch. Heaviest trailer (cargo) I towed was about 9000lb with tongue weight around 950lb. It was WAAAAY over the limit, but I realized it too late - when I was already on the road. Trip was 4500km (2800ml), X5 was towing it amazingly well! Though, I would not do it again!
Nothing was bent, nothing damaged. Invisihitch survived it very well. As far as I understand it, Invisihitch is class IV, and on some stronger car it could have been rated up to 10,000lb.
Now, I am going to be towing trabel trailer of ~6000lb, but square area of sidewall is huge (possible sway). Thinking about WDH mostly for their No-Sway function. Andersen No-Sway hitch from iamthestig's post looks perfect!
Btw, about BMW hitch - isn't it rated much lower then Invisihitch? Only 5000lb at most? Not an option for me
(empty trailer on the photo: )
