Clamp on derailer for C-40

[rinconryder]

Is it possible to use a clamp on front derailer on a Colnago C-40 frame with a braze on? If so, does anyone know what size clamp I would be looking at? Thank you in advance for any help!

[wasfast]

The braze on will be right in the middle of where the clamp is supposed to go. Why would you not want to use the braze-on?

[rePhil]

And as long as the brazeon (riveton?) is there, it won't work.