Hi Andrew,
I encountered a similar problem with my contemporary Ron Cooper built Bates Cantiflex, plus a newly acquired Rauler racing tandem. Can't understand how Mr. Cooper built the fork this way, as I specified short reach Campy s idepull for the component specs???
Front short reach brakes sat too low for the pads to fully contact the rim, thus I modified a Campy drop bolt to serve as a reverse elevated brake cen ter bolt. The modification simply requires cutting/filing a spring slot on the opposite side of the conventional spring slot. Not aware of Campy making a long nutted front drop bolt, so you have to use a recessed allen nut on modified rear nutted drop bolt,,,,or find a standard nutted front Ja panese copy drop bolt,,,,these are pretty tough to find!
Here's a link to a Wool Jersey photo that clearly illustrates what I did to make the brake work on my Bates:
http://www.wooljersey.com/
Hope this is helpful.
Regards,
Kevin Kruger - Grantville, PA