Need to buy a new helmet (getting back into streetbike riding after years away) and I have seen some that flip up at the front. I seem to recall these first appeared as BMW helmets and obviously others have since copied. I don't need one that "converts" to an open face helmet, but rather just think the flip up front would be convenient. How easy are they to "flip" ? I get hay fever would I be able to flip it up to sneeze rather than spray snot all over the isnide of a full face helmet? Anyone own or have experience using one of these can discuss pros and cons?