I am experiencing a situation where the chain rubs on the bottom of the FD (underside of it) when on the large ring and 29t rear cog. It is not chain rub on either side of the FD, as raising the FD up eliminates the issue and I can see it is rubbing on the underside of the FD.

When set up so that there is no rub on the 29 cog (vertically and internally) the FD is up so high the front ring shifting is unreliable (chain drops far too often when used without gingerly dealing with this issue while shifting). I can get an acceptable performance on all but the largest (29t) cog.

This is a braze on FD, and the hanger on the bike is perfectly aligned. All parts are campy chorus. Seeking suggestions of how to deal with the FD I have, or seeking input on a FD that allows the 29t to work without this annoying rub and keeps the chain reasonably well put when shifting between rings.