The front holes needed covering. A layer of medium silkspan works fine and adds practically no weight. The side hole is there for the ignition wire

The exhaust louvers on the bottom of the cowl are easy to cut and shape with some help from a monokote iron. Simply heat and bend. That should be all that's needed to get engine heat out of the cowl. A slight negative will be created by the raised flaps thuspulling the air out. A large amount of exiting area is not required; with this type of treatment the old 3:1 rule of thumb for exit to entry area is not necessary.

Talking of cutting, I re-discovered X-Acto saw blades. These make hinge slotting really simple. They are the same width and thickness as a #11 blade, just perfect for Radio South and other ca hinges. Of course they have other uses</p>