Prusa i3 MK3 Part Cooling Fan Duct Remix

Simple remix from KevinTheGoalie's remix of RoboGenius's fabulous MK2/2S blower fan duct. All I did was add a "rib" down the center of each air channel to provide support for the top layers as they print. My attempts to print KevinTheGoalie's version in ASA and PETG would droop quite a bit & wound up with a lot of filament loops inside the part that I couldn't easily remove. Probably wouldn't have hurt anything to use one of those, but I decided to make this mod & print it. Worked fairly wel