Theoretically weight outside of the wheelbase hurts polar moment of inertia which relates to on the limit and turn-in dynamics. But it also helps take some weight off the left front corner. Sometimes that can help more than the polar thing.

For example, some camaro autocrossers use very heavy rear tow hitch assemblies so they can exit corners better. It would be interesting to play around with this factor on a test course.

The stock M3 battery tray can fit regular and extra long batteries. I think that the long ones weigh something like 52 pounds.

Stan