Basically the figures that George mentioned were quoted in the source.  However (big however) what may not have been clearly pointed out was that the major part of the reason cooling effectiveness (not efficiency) increased was that inclining the heat exchanger permitted you to install ever larger area cores in the same size duct.  So the increase in cooling effectiveness by inclination was in large part (like ‘entirely’ – my words) due to the larger size radiator permitted by inclined placement in the duct.

Yeah; that’s it.  Thanks, Ed.

With modern high density cores, basically straight thru is best efficiency and lowest weight.

Al