Has anyone done any trailer towing with either the 428i X or 435i X automatic? Curt makes a 4 Series specific class 1 hitch that mounts with no drilling or cutting, but my BMW dealer tells me towing isn't rated or approved. I have need to occasionally tow a motorcycle trailer (800 lbs.) and one motorcycle (550 lbs.) which I've been doing with my 2003 Jetta GLI VR6 (manual), but with 181K miles on it, may soon be retired. I'm not concerned about voiding warranty because the 2014 428I X is already out of warranty, but like some confidence the BMW can handle towing duties with cautious use.