RJ has it going on w sizing. It'll put you into an 8"HO or even a 10". The filter should be a Can 100 or equivalent. Might want to get a speed control to dial in your air flow.
Just a variation, but if are really concerned w odor control, look to using your fan set-up as a "push" system... you have your fan hooked up directly to the scrubber which sucks all the air in. This then pushes the clean air through all of your ducting/cooling hoods & evacuated to your vents. The idea is that all the air going through your ducting is trying to push out of the leak/holes/connections. If you run the fan at the end of the line (pulling the air), air tries to get into your ventilation through those leaks... which is unscrubbed air.
BTW, shit you not, can't find any evidence that supports Ona's claim of molecularly neutralizing odor particles. IF it really did do that, why concentrate it with a masking agent (the fresh linen crap)? All you can smell after putting your nose to it is Ona, granted no weed, but that is through masking. That pine suggestion is the same thing. Don't trust masking agents. Peace.