hi - bath fan on my to do list. Got the parts (including 4" galv duct), a couple of elbows, fan, etc. I lined everything up on the floor to sanity check the run, before dragging parts to the attic to install. The vent hood at the wall has an integrated section of 4" duct (@ 12" long) - it's crimped on the end which implies all my pipe will have the crimped ends facing into the airflow. I have @ 12 feet of horizontal run to get to the gable wall where this hood will be installed. I thought about cutting the (crimped) end off the vent hood extension to keep all the crimped ends oriented with the airflow. Does this really matter? What about a dryer vent (e.g. will lint / stuff hang up on the crimped ends inside the duct depending on the orientation of the pipe?). Just curious.