Okay I see. My fan didn't come with a mounting point on the bottom. It has two metal straps with a 90 degree bend near the end with a couples holes drilled through. I had to offset my 2x4 lower yo allow the straps to sit right. Got it all attached now. Still loose in the hole of the hood...
thanks for the pics Dolomieu. So you have the fan housing thru the hole in the plywood end of the hood and not attached other than with caulking? The hole I cut for the fan is slightly too large so it isn't a friction fit even.
Your pics are kinda dark (sorry for being picky) so I can't...