Don't Pauls make a weird type of canti that will adjust for anything between a 26er and 700c on the same frame??? It probably costs as much as a frame, but -

http://www.paulcomp.com/motolite.html

A polished collar fits around the arms and holds the Kool-Stop brake pads in place, while allowing them to be finely tuned for height and toe-in...



Hmm... List price is $125 a wheel. Which is more of an ouch than a hmm, really.