[Tommy]

Kevin,

It's hard to tell from your post whether you've figured out everything about your brake system except the number of pistons, or if you think that is the only brake system issue that matters. The most important thing about pistons is the total area they cover. A larger number of smaller pistons merely allows you to get more total piston area inside a smaller diameter wheel than a large piston would require. ... So I suggest you get whatever number of pistons in whatever size they need to be to both stop your car and fit within your wheels.

If you haven't figured out all the rest of your braking systems requirements (e.g., rotor diameter and thickness for stopping torque and heat dissipation, pad material, master cylinder diameter, pedal ratio, etc.), you need to do that before you finalize your piston decision.