I haven't got there yet, but planing on both panels, sometimes you'll have to open up the cowling a bit to relieve any additional pressure that cannot be relieved by opening up the lower aft panels. It seems that in that post he had a fairly large opening for the intake and fwd of the exhaust. I'd imagine there is a lot of turbulent air in that cowling that isn't escaping efficiently enough to cool down the engine... Hence why he closed the gap by the exhaust. So sometimes a 3:1 rule needs to be a 4:1, just depends on how easy it is for the air to escape the cowling. I like to imagine as if it was fluid moving through the cowl rather than air, it's easier to visualize baffling that way for me. Unfortunately this is hard to do with a single cylinder gasser. But bear with me and visualize squirting a garden hose into the intake, where is the path of least resistance? Right back at you? Or is it out the aft lower section where it needs to go?