Ah, I hadn't considered the height of the caliper... I thought it should fit around my wheels as I'm using 700x32 tyres rather than anything hugely wide (I figured if I was going to put 700x50 or something on it then I might as well stick to riding the MTB).
Maybe the best bet is to just swap out the rear brake with something easier to work with, something more like the front brake.
__________________
"For a list of ways technology has failed to improve quality of life, press three"