I plan on making one more of these for taking out heat form the room. The second one will be mounted on the ceiling (as heat rises) and cut a whole in the wall to the attic just big enough for the 8" duct to fit in, obviously tape around the duct & hole to seal it off form outside elements coming in. I will have about $55 total invested as I wont need to purchase another roll of duct tape, for 2 fans, an incoming fan and an exhaust fan. Works absolutely perfect and for about 1/3 the price of a single decent inline duct fan.
The fans do have a single screw mount option on the base, so is very easy to mount... put a screw where you want it, leave about 1/8th inch from the wall, slip into hole on base and slide to lock in place.