Never measured rotors on either car. Maybe if I have the wheels off, I will. Both cars use the same wheels so I don't think there are any clearance problems. Do both your 126 and 107 use exactly the same master cylinder? Same part number stamped on the unit? If not, could be different presures. Also, with ABS involved, I would be wary of changing the design of the system. My wife's SL stops very quickly. Granted the 126 probably weighs 400-500 lbs more than the 107, but I still don't know if it would be a worthwile swap.