That's kinda the info I'm looking for as well really, although I can get 4 pot calipers very cheap so it would be a waste to not take advantage of that, not to mention the weight savings compared with retro fitting from another car.
I'm looking at running a 25mm disc, between 280-285mm diameter, but at the moment this isn't much of a concern because the 4 pot calipers I'm looking at (AP Racing, Alcon and even Wilwood) allow me to run anything from 250-310mm disc diameter) The only doubt I have with running the 25mm disc is that the car will be used on the road as well, so keeping heat in the brakes might be tricky and leading to running a lot of front bias. Although this could probably be sorted by running a street type pad, then swapping the pads out for something more orientated for racing.
Hmm talking about the 57.17mm diameter single piston, that makes me wonder what size the master cylinder is for the starlet if it's easy to lock up. Because that's ultimately what I'm trying to achieve is to balance caliper piston area with master cylinder size.
I've been working out piston area sizes for a lot of aftermarket calipers, I know greater isn't always better as you lose the feel in the pedal, and if you go too small you get shorter pedal movement but obviously not enough power. I think I'm going to send my findings off to someone like AP Racing and see what caliper/piston size and master cylinder size they recommend for the mass of the starlet, power etc.