A word of advice if you are planning to make your own flaps: Make sure they are either not as strong or not as stiff as your fender. If they are, the next time you wheel your off a curb or set the bike down on the fork tips and forget the flap is there, that flap will break the fender at or just above the flap attachment. (Bending or breaking when a stick gets jammed in it might be kinda nice also.)

I've been making my flaps from doubled up graphic film taped around the edges with clear packing tape. They last several years and fold back easily when hit. My supply is running out soI may have to change my ways soon.

Ben