Background info: I have FD RX7 (16") rims on the front at the moment, with the longer IS300 studs and a 10mm hubcentric spacer (because the FD rims barely rub against one of the control arms at full lock without it).
Picture of stock caliper:
I took off the passenger wheel and caliper, left the stock rotor on and test fit the caliper to see where it would lay. Picture:
It *does* fit underneath the FD rim. However, it is barely rubbing against the spokes in the picture (as in, I can press the wheel against the hub and move it and it barely scratches the paint on the caliper). Kind of annoying. Since I have a 10mm hubcentric spacer anyways, I'll go buy a 20mm hubcentric spacer which should give me more than enough room, and with the longer studs that won't be an issue anyways. To be honest a 15mm spacer would probably work but I don't want to return it for whatever reason.