After printing and installing Edgrico1's excellent fan duct, I noticed that mine had a bit of a drooping issue. It still worked, but the duct was uncomfortably close to the parts being printed. I added a small tab which hooks into the stock extruder housing to help hold it up.
Make sure you print it in something that won't melt under normal usage; the one in the pictures is printed in nylon from Fishy Filaments.
Fishy Filaments Nylon