Mailman, you have no rub with the 205s on the front?
I just bought a stock 453 cabrio with the sport package hence 16" wheels, and I actually lost control of the vehicle for several seconds during the drive home while on a connector ramp with a fairly extreme curve. Discovered once home that the dealership, in rotating the tires, had put the 205s on the front and the 185s on the rear. That's when it occurred to me that the sensation I felt in the vehicle when I lost control was that a wheel had made contact with some obstruction.
I believe your issue is not rubbing but having more grip in the front than the rear.
MB designed the Smarts with thinner tires up front, thicker tires in the rear because they failed the 'Elk Test' with their small A series model.
Basically, you turn abruptly and the fronts are supposed to break free first, so as not to roll over.
Stock rim widths go as follows:
450 Front 4.5 Rear 5.5
451 Front 4.5 Rear 5.5
453 Front 5.0 Rear 5.5 (15")
453 Front 6.0 Rear 6.5 (16")
The 453 was designed with the least amount of 'understeer' with only 0.5" difference between front and rear.
So in my case with 205s up front, I chose (and located in Europe actually) 225s for the rear, preserving the 1" tire width difference.
The 'spec' sticker on the tires in the picture above is USA on the left and EU on the right.
Interestingly, the EU sticker has the '71db' at the bottom for tire noise.
I looked up the EU sticker for the stock Contis and they are '94db'!...