The rule of thumb for a 12 inch duct is 715 cfm. You would need a 20 inch duct to handle 2000 cfm.

I assume you would either buy and fabricate a bracket that would allow you to install it inside a 20 inch duct.

Why are you tying to accomplish? Booster fans usually can't overcome a poor duct design.

Mike,

Are you not talking about 715 cfm being max in a HVAC application?

Looking at the fan identified in the OP it is a whole building or space exhaust/supply device - 715 cfm is not a limit in that case.

No hassle, just asking.

I am going by the chart I found at the link listed below (see lower right hand corner). I believe the sizes are calculated for a friction rate of 0.1 wc or less.

I assumed this was for an HVAC application. If the application can allow more friction, then the air flow can be higher.

I would think squeezing 2000 cfm of air through a 12 inch duct is very noisy.

Here is a link that might be useful: Rules of Thumb for Duct Systems