ScottG wrote: "Based on your experience, opinion or "just what looks right", I would like to know your thoughts on which style you think would allow more draft."
I repaired/replaced my cover several years ago. Mine (Dometic) is more rectangular size like 12" x 26". I noticed significant heat coming out the cap also but keep in mind, getting too much flow may cause flameout issues when driving or in heavy wind when parked. It's also an easy entry for critters. Unless you have specific issues with refrigerator function, I would leave it alone. More flow isn't always better unless you listen/read too many K & N air filter ads.
Chum lee