I have 3 Spec1-r helmets.... the Capirossi (mine) the hawaiin flower (wife's) and the Xaus (I bought for a friend)... they are a little loud, but then again I have a Jardine RT1 with the race baffles so it is loud...
As far as in between sizes..... the cheek pads are interchangeable... if you are in between sizes, get the smaller one and change out the cheek pads... I normally wear a medium helmet, but in the Suomy the medium was a little tight and the Lage was a little big so I bought the medium one and bought some smaller cheek pads... fixed the problem.. only problem is the cheek pads are a little expensive, but I figured since I got the helmets at a ridiculously low price, I ordered the cheek pads and still didn't pay anywhere near the retail price.... hope this helps
Oh yeah, I have pics of my lids on one of these threads.. I think it was the thread about lightest helmet...