Ha, that's the million dollar question: I used to get the odd bug around mid-top of the face-plate, now I get every bug full in the face and the wind is hitting just below my face-plate and getting a bit around the tops of my shoulders too... Cant complain tho' - cos the buffeting is 'gone'.
No added noise, the Shark Carbon R is extremely quiet on naked bikes, just a little noisier on the K bike but I wear silicon plugs anyway.
I remeasured for you - and yes, it is just on 3" - maybe 3 & 1/8th... Have fun, be brave! Cut!