Basically for larger systems I would simply go bigger than you may need, ideally it would be controlled by a some kind of temperature controller so you couldn't really go too big. Larger fans should be used, you probably wouldn't be able to get away with computer fans for larger units.
Also FYI, I tried using gutter guard instead of eggcrate and found the eegcrate to actually work better. It's less restrictive to air flow and it produces just as much surface area for contact if not more. A finner mesh will only increase the surface contact between the mesh and the water, not the air and water. It's not a bio-filter
