To see the difference in vehicle mounting with OE and aftermarket hitches, look at the BMW instructions here: http://www.bmwmotorsports.org/pdf/e5...iler_hitch.pdf

Look at section 2.3 to see the reinforcements BMW uses. Some hitches just bolt to the rear pan. Others attach at the same point as the OE hitch but don't use any reinforcements. The reinforcements tie into the longitudinal box sections in the unibody and are cross bolted in three planes.

The instructions show the Euro hitch but the mounting is identical

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue