I just reread all of these old posts, I had to ditch the elec set up and go to a full shroud and mech. fan. The 1/2" thick shroud on the elec fan set up didn`t pass enough air over the entire rad core , just like RRR said.
I have a lot of h.p. and can only run a 17' fan, due to room , and cant even loose the airflow needed with a clutch blocking part of it.