Once at a big BIG cruise in Sweden (Vesteraas) there was so many us-cars (10.000+) too many to cruise -only traffic jams) -I ran so hot that my accellerator pump melted!!! -Now THAT is TOO hot!
(everybody was 'cruising' with an open hood -w. a beercan up front to keep the hood open.. ;-) )
-the old 350 buick was running an idle at 650 rpm's but it was too low ,-when 'cruising' was actually sitting in a biiiig traffic jam, -having fun though...
-that was with a mechanical fan, and they only run as fast as engine is spinning, -so maybe that is another factor?? -Also, try putting the old fan on, -my bet is that the flexfan isn't cooling enough.
Just a thought..
Ohh, and if you don't like running with a stat. -put one in anyway, and drill just a 0.200 hole in it.. -or a little bigger.. -160 degrees is recommended.