Decided to use the 5 1/2" rings and the fiberglass parts that came with the Sam James Cowling. The reason for the change in direction is two-fold. First, I will increase the air inlet area to the radiators by adding 4" round inlets below the Sam James rings. Secondly, I paid for those items, and I want to use them. I believe they can be used without sacrficing engine cooling -- if I plan things out properly. Cut the holes for the rings. Also roughed in the vent for the oil cooler.
Rings and vent for oil cooler roughed in
A look from straight on. I prefer the look of the round rings.
Another angle. Also visible is the filed area where the cowling halves meet.