Bill invited me to come up with a solution to this problem. I suggested adding a second oil cooler mounted in series with the existing oil cooler. I turned up with one mounted in a specially made duct with the intention of hanging it underneath the fuselage.
After looking at the plumbing and also considering the pressure loses across the second cooler we abandoned the second oil cooler option. (The fact that the primary cooler has a by-pass valve that might open if the second cooler was more restrictive could lead to disastrously high temps possibly while the pilot was too involved in pulling G's to notice). There was also the desire not to add significant weight or to make large scale changes to the structure of the airplane.
After some careful thought, Bill and I implemented a very simple but effective oil cooling solution using just a few dollars worth of parts.