Interested to have input from the list on cowl inlet sizes, and if
  anyone has increased the diameter, and how that has affected the CHT
  cooling.
  My O-320 has the prop control located inside the left cowl intake, and
  it seems to me that it affects the intake flow by a large percentage.
For example, cyl 2 CHT, given its location relative to airflow, is the
  hottest cylinder.
  Photos of any cowl remodelling would be appreciated.

Dom,

 

Cyl 2 CHT used to be my hottest.  No longer.

 

If you look at where Lancair positioned the bottom of the baffling as it comes to the head, note that there is about a 1/2 inch bend up to lay against the head fins (just keep you focus on the upper head, not the barrel).  If you also examine the cyl, there is a flat spot at the forward edge.  So, no air that curls over the lip can pass downward and over the fins below the flat area and the lower plug.  Your actual situation may vary slightly since I have ECI cylinders but look at it anyway. 

 

I redrilled the few holes in the base plate of the baffle to move the aluminum that wraps the fwd lower head fins forward by 1/4 to 3/8 inch.  I also bent the edges of the lower wrap so that no air could escape from the sides.  Then I cut that upward flared lip off.  Then, I made a small deflector that sits about 1/2 inch above the base baffle plate and directs the air downward into the space created as noted above.  This dropped the head temp 10-15 degrees and is now more in line with others.