those gxp s300's should have supplied spacer rings that go inbetween the cups and the bb shell. throw those on(or get some more) and it will move your chainline out but the millimeter or three of clearance you gain will be worth any slight(read: barely perceptible) chainline issue it causes.

same deal with my ftp. spacers work wonders, its IMO one of the best advantages of the external bb design.