I am having quite a bit of issue when i'm cross-chaining (50x11t) when using my 303 tubular. The body of the derailleur is hitting part of the spoke (closer to the hub rather than further down), and simple addition of a cassette spacer is not helping.

I called up Zipp and was told to go to a dealer, except i have taken it to a shop and the shop couldn't do much about it either. Anyone have suggestions as to what i could do (i also changed the B-screw without much success)?

Fwiw, this happens only on my road bike (Scott Foil) and doesn't happen on my TT bike (Scott Plasma)

Many thanks in advance