Next time when you're measuring stuff take a caliper and not a ruler.
Piston size from a EK9 caliper is NOT 55mm but 57mm.
You can even see on the picture that your ruler is off by at least 1mm on the piston.
Ill give you an A for effort, and an F for bastardizing our Honda with inferior brakes
Seriously, nice job. However I will mention this. Im willing to bet that the CTR brake setup will outperform the R32 brakes. Same rotor size, and yes the Nissan caliper is a 4 piston, but the pads wear and taper, In fact, the single piston CTR caliper has less taper wear. The pad is also a better shape than the R32 caliper. Basically I think Nissin > Sumitomo in brake design. As a whole, Nissan's are prone to brake fade because they do that same recipe every time (even today) by giving a big thick rotor but making the pad and caliper too small and too light respectively. The pads overheat and the rotor isn't sucking up enough of it because the caliper gets too hot. I see the aluminum caliper body, which will heat up faster and its heat vanes will help somewhat, but I've driven a 300ZX with autozone ceramic pads, and my EK sedan when it had CTR-4x100 brakes with the same autozone pads and my car would outbrake the Nissan, regardless of what tires were switched on or off, and in spite of the 300ZX (same caliper as that skyline) has bigger rear discs with nearly identical rear pads to the CTR.
Not meaning to rain on your parade, just defending the CTR brakes as awesome.