This sounds like a problem with flex in the fork and brake bosses.
There is always a problem with making things as light as they can be. Sooner or later someone that is a little heavy handed will really screw your planning up.
At least one of you Cannondale folks should try using a Brake Booster. These are made by several manufacturers and you can get aluminum (AC Products) or Carbon Fiber (Salsa) from several places.
No guarantees this will work though since cantilevers are liable for these sorts of things anyway.