That's quite a bit of difference, and a lot of cantis probably won't handle it, though undoubtedly some will.

I just started a thread yesterday to try to gather measurements on people's successful wheel-size changes involving canti brakes.

In my mind - and I'm new at this, having only started thinking about it yesterday - the measurements that will determine success or failure for any given set of cantis include:

- distance from wheel axle to canti posts
- distance between posts
- rim width, since the pads are descending as they squeeze towards the rim (ie: the pads will be lower by the time they contact a narrower rim)

If you take on this project @hat and beard, and make it work, please post your results to that thread!