Not super easy, in my Prizer Pro-Line, it's basically 1 blower for 600 cfm and 2 for 1200. Also the vent piping w/600 cfm would probably be 7-8", you'll need 10" for 1200 cfm. I went w/1200 for my 36" BS and a 42" hood, I don't wish to smell yesterday's fish or clean cabinets anymore than I need too. If you put larger vent pipe in up front it would make it easier but I don't know about switching out the blower.

I'm going with a 36" 6-burner BS rangetop with a 36" Zephyr Tempest 2 hood with dual internal blowers for 1200cfm. The house is currently being built so I cannot comment on effectiveness. As well, per code we need to install a make-up-air system.

I know that 10" is preferred for a 1200 cfm blower, but I only had room for an 8" duct for my 1200 cfm blower in my hood. I have a 42" Modernaire hood over my 36" Blue Star RNB. It works fine, albeit a bit noisy (actually a lot noisy) on high. But it only runs for a few minutes so the noise is not a deal breaker. I don't think the duct diameter should be a problem if swapping out the blower is possible.

Under some conditions, adding a roof blower to a system that has a hood blower would significantly increase flow. Control would be the big issue, and requires that both fans use the same type of control, and that the control used be able (or be swapped with one able) to handle twice the current. If you are getting a tailor-made (bespoke) hood, you could order a suitable control for the initial configuration.

Both fans need convex fan curves to avoid any hunting between fans.

The pressure losses through the baffles and restricted duct, along with any MUA restriction, would determine the actual flow rate.

kas

I went with a 36" hood over my 36RNB with griddle, but only because my range is a peninsula, (Iknow, a GW no-no) and I did not want the hood hanging out over the end of the range. I have a 1000 cfm remote blower on an 8" duct because of tight roof framing constraints. It is sufficient for most all cooking, except occasionally when cooking something very smokey, (Italian Sausage for example), a little bit may escape the capture area. I'm sure a 42" hood with a 1400 cfm blower on a 10" duct would be better, but It just wasn't doable in my situation.