My limited knowledge in brake hydraulic design tells me that if the total wet area of the pistons in the 4 pot calipers is greater than that of the 2 pot ATEs, then pedal effort will actually decrease. With more pedal travel though.
What model Bimmer did the calipers come from? And do you know the piston diameter?
Loosing the weight of two high mounted boosters certainly won't hurt the handling either!
