Half an inch is the old saw. Ideally, this will approximately match the linen showing at the jacket sleeve. Now, if you fancy 3/8" of linen at the cuff, as did JFK, then what to do at the collar? Maybe someone will favor us with a photo...That raises the question - how much shirt collar should stick up above the coat collar traditionally? None? half an inch? I don't know off the top of my head what's really normal, is there a normal?