I had the HJC Sy-Max helmet. The instruction said "DO NOT RIDE WITH THE LOWER CHIN BAR IN THE "UP" POSITION". How about the GMAX? I have the GM68, nice stuff at a fraction of the cost I like this.
It has a generic "Owner's Manual" that doesn't say a thing about not riding with it up...not a lot of wind behind most Concours windshields...so, I guess it would be up to the rider/wearer...