Some questions on 600W setup

[GaGrown]

What's an average CFM needed for cooling one or two 600W hoods?

With 1 600 watter,I used a 265 cfm fan. Now with 4 600's I use a 265 inlet and a 265 and 465 exhaust. Really need to have 2 465's.I have 4 Pro Ultra lite hoods.Great hoods and very versatile with not alot of headspace.

Ga Grown!