Under 16's!!! Jesus!
I've got 300mm ST170 discs with Mk3 Mondeo calipers already fitted, I fit a set of 16s for general moving around and loading/unloading off the trailer and the current brakes look pretty tight under those, couldn't imagine another 30mm of disc size PLUS big 4-pot Brembos under there.
Great that they should fit under 17s though, would make my life significantly easier! Will post up some pics once they're on.