Ahhhh - largest I've seen was a 16" which is taller than the radiator on my 2.0, but narrower - 2 x 10 pullers is what I have been considering, not only do they move more air (cfm) than a 16", but they can be run in series - half speed, less cooling, less noise or in parallel for maximum airflow when necessary.
This is how it's done on the new (second gen) Grand Vitaras, where the fans are controlled by the ECU.