Ed,

 

Do you recall where you got your (now un-necessary) louvers?  I am going to try an area at the top of my cowl.  Can't seem to find a source for these louvers.  I need 12" X 6" with the cuts going the long direction.

 

I ran a test today and found a minimum of 2" H2O trying to force air OUT that area.  That was with my cowl flap full open.  (MUCH more pressure, of course, with the flap closed.) 

 

Does anybody think that will make a significant change in cooling air flow or am I wasting my time?