This has been around for a while. Caliper uses wrx shape pads, which are small and comparable to our stock pads. I dont't know if they match the swept area by the stock pads, as I didn't research further. If they don't, effective radius will be bigger, which means brake torque forward is increased and so brake balance is affected. I think it is generally difficult to create a fixed piston caliper for the stock rotors because of pad choice.