I'm with you, mine wasn't straight / aligned with the wheel axis. I think that the shape is more likely (as opposed to something like a motard fender) to create the dynamic imbalance that will allow incorrect chassis set-up to come to the fore as headshake. From my understanding 2 things must be in place for headshake to occur: incorrect chassis set-up and a trigger. The trigger could be corrugations, aerodynamics, whoops, strong aceeleration that gets the front end light, etc. The focus should really be chassis set-up, as the triggers are likely to be part of off-road riding.