I wasn't satisfied with the standard "rubber lip" sealing to the fiberglass cowl for reasons of poor cooling, airflow leaks, and also engine heat could discolour and distort the paint on the upper cowl half. After researching fiberglass plenum's on the internet I decided to create my own. Step 1 was to build a form in place on the engine using wire and duct tape. Step 2 was to lay 6 layers of 8 oz. fiberglass w/ polyester resin onto the form to make a baffle plug. Step 3 was to build a framework and fiberglass it to the engine baffle so it would not distort when I removed the plug from the top of the engine.