put your ear on the driver's side window and try to wind the driver's side mirror out until you can just see the edge of the car. will it let you or does it hit a stop before it gets there.
try it with the seat 2/3rd of the way back for the taller among us.
don't know how tall you are, but . . . put the seat up fairly straight, sit up as tall as you can with no gap between you and the seat. how much space is there directly above your head? (nice to know your sitting height too when you're doing this, but at least a rough guess on your actual height will help.)
Yellow RX-8 GT w/Nav, Arch Spoiler, Splash Guards, Rotary Accents, 6 CD, strakes, bezels, sills, filter; still want fuel cap