Welcome to the silliest, awesomest, bestest bikeforum...

SPDs have a similar sized contact area, and not many people are complaining. I'd think comfort depends more on the shape of the sole and the kind of insole you have. 'Course, a stiff sole can't hurt.
Are you a messenger? 300+ miles is a lot...

Edit: I'm pretty sure that the frame aroud the candies will not touch your shoes, or only just. Don't think it will add any support. Otherwise, how the hell do you clip in/out? That silly thing is designed to allow you to ride in street shoes if you must, but I hear it's pretty much useless at that as well. As to the quattro, I have reservations about that, too. Anyone used them?