My opinion (not data) is that if your cooling problem only occured on the
ground and not airborne then cooling fans MIGHT have merit.  However, at
flying airspeeds they might hinder airflow through the radiators more than
help, just hard to tell.

===>  Hopefully, I'll have some info on this soon.  I have a 16" fan on my
radiator.  I figure that I'll get some good use out of it on the ground, but
I'm not sure what good it will be in the air, particularly since I have such
a large intake scoop. It's located on the outside of the radiator, so it
also serves the purpose of keeping the radiator from getting hit by fod that
might be picked up by the prop.  

===>  The only time I can see the fan being useful in flight, would be if
you had your ducts sized so small that they worked for cruise, but not climb
speed.  There would also be some initial climb use value if you can use the
fans to keep the temp on the low end prior to departure.  In my Lyc powered
RV-8, I did everything I could to keep my pre-departure cylinder temps as
low as I could.  This really made the difference between red-lining the
temps, or not during climbout on a hot day.

Rusty (W&B today, it's going to be a pig)