So I purchased a Louis-Garneau Chrono-Leggera helmet, and then purchased the add-on visor for the helmet.
However - when I put the visor / windscreen on the outside (i.e. - rather than slide the windscreen in-between the helmet cover and the Styrofoam), there is a gap between the helmet and visor on the front.
When I try to slide it in between the helmet cover and Styrofoam, it will not fit.
I just want to check that it should go on the outside, and was hoping that this gap is normal (does not seem very aero, but then again, it is more aero than just sunglasses.