To be honest I have never had a chain rub on both the 1st and lowest (6th, 7th, or 8th) cog without an adjustment problem. As others a said , generally you adjust the derailleur for the large (outside) chainring to run with the smallest cogs and the small (inside) chainring with the largest cogs and let the trim occur as you move across the cogset. Keep in mind that using all the cogs with the same chainring does result in chain crossover.

I have done a few things to adjust it that may require a small height change, or slight angle, or maybe adding a washer to spread the cage slightly. These are just small tweaks. You may want to see if there are any other Campy FD that will have a wider cage or mod it as described above if you have the intestinal fortitude.

John