vents

I just ordered 4 vents from Van, the kind that hinges out into the airstream, I guess they are relatively new items. I am planning on putting 2 on each side of my RV4, mounted in the side skins, 2 for the pilot and 2 for the passenger. I don't think they will fit in the skirts since the skirts are not flat. Does anybody have any input on this like how much cooling will I get? I am under the impression that the NACA vents don't work very well, is this correct?