this is looking better in the last picture.

The trick with cooling air is that it needs to hang around a little in order to achieve heat transfer. Air is not a good geat transfer medium.

The tricks I use is a large air inlet that is followed by a larger volume behind the inlet. This slows the air down.
If you can then channel the air through a exit that is smaller than the volume inwhich the block and head sits but diverging to the fuselage exit you will achieve good air extraction.

The general rule of air inlet must be 1/3rd the size of the exit is not a good one IMO. Look at race cars. Thy use a certain size inlet, sculted air flow pathways under the body to exit at a vent that is usually of equal area or less than the inlet.

I understand this may be controversial