Originally Posted by Bob Ross

Obscure trivia: Cannondale's "SI Integrated" carbon forks & headsets & expansion plugs etc (the hardware for which iirc is OEMd by FSA) explicitly state that you should not use any spacers above the stem. I haven't looked at their design to figure out why they are so emphatic about this point, but it's slathered all over their installation guides and owner's manuals enough times that I'm sure there's a reason either their design team, or their legal team, insisted this be stated unequivocally.