I'm not sure if it's too late for Woody's unit, but one simple (but slightly time consuming) mod if you have the cooler out for a clean would be to dremmel burnish the inlets and outlets of each of the little capillaries so that they arent a flat sharp entrance, but rather a rounded face facing the incoming/outgoing air - we call this in the business the "kv loss factor" and has a marked improvement on entrance and discharge losses.

It wont improve cooling but it will reduce dP (pressure drop) a little.
Post Script - after analysis resulting in the later post - this will only hlep water dP, not air dP