A real lazy guy could make this work using a standard paper stapler instead of sewing.
I doubt im going to read 14 pages in this thread im only on page 4 but how about just packing the carbon in a womans nylon.
I went and got one of these and a 6"-4" reducer duct put a few filters in it and duct tape them in the middle then tape the two together and viola. you have a can filter and fan combo for about 42 dollars sweet I know they are about 150 at a hydro shop. also if you glue the scotch towel together I am a fan of loctite stick n seal they look like I should manufacture them and sell them and you don't have to have needle and thread skill. I love you pan but I am a lazy man.