Again I have to disagree, I could have all the coolant flow in the world but no fins (as in only the surface area of the tubes to transfer heat) and I'm not going to transfer much heat from the coolant to the air.
Air cooled engines have no coolant flow (no coolant) but they have a huge surface area due to the fins on the cyl walls and head.
Not one single thing is more important in radiator design. It is a package and a dance between (no particular order) coolant flow, contact area, fin count, material, tube size and count, etc.
Still waiting on the OP to post up some photos of his current setup.
