I believe totally in what snaps says. It's the same thing with a dryer. If you use the shitty flex lines, they create baffles in the line that disrupt air flow, they trap dirt and debris and are not the best option. I am not sure exactly why people don't use rigid ducts.
You convinced me. I just replaced 4" flex with galvanized in my GL60. I can now run the inline fan at a slower speed to maintain a good temperature (78F) This results is a quieter bedroom closet grow which is what I was aiming for. Thanks
I cut the hole in the ceiling to be 8" in case I needed to upgrade it. Thus, what you are seeing is simply some plywood cut with a 6" whole and screwed on with an identical one on top. The holes are cut fairly exact and a piece of PVC goes all the way through and there is a collar on the roof side that slides over the PVC and holds it in place. It is also caulked, top and bottom.. This is a bit blurry but here it is coming out of the room roof.