It's a 6" im almost certain now that i can see it good. Measure it. If it is your fine if it isn't a 6" fan would help. I would make that intake double that size for your particular setup. And I'm tellin you that plastic strap from lowes comes in 25' length by 3/4" wide. Get a pack of anchors if it's drywall or screw Into studs if you can and hang fan/filter right above the exaust hole sideways quick elbow out the hole. Put it up high hanging from ceiling to get it out of the way. I guarantee if you open that intake a bit and have virtually no duct you'll be good.