Nice setup, thanks for sharing. On the 453s the MB instructions are to disconnect the negative side of the battery. It's a minor nuisance because without any power you have to re-set the clocks and radio pre-sets every time you tow but I guess that's better than having the ABS, ESP or worse the transmission engage when you least expect it. We use the RadyBrute Elite Tow Bar with the mechanical built in braking system and a Blue OX baseplate & diodes for the tail lights. The mechanical braking system has cables that run from the tow bar to the brake pedal, a simple system that works really well. HOWEVER, when attaching the brake cables to the brake pedal you must leave a little slack in the cable or the ECM on the smart will think you are driving with the brakes on and will put the car into limp mode.