A slightly different twist on the fan mod
I printed up Stu Ritter's instructions and took them to my independent. Instead of drilling a hole in the bimetal strip, he simply used the screw-on top from a spark plug, ground it down to about 3-4 mm high, and slipped this over the pin and then put the bimetal strip over it. It is now bowed UP due to the spark plug ferrule. It has the same effect as Stu's fix but is a little easier to get on and off (we think), since you want to be able to disable it for winter.
Makes a dramatic difference in engine temp in these days of high ambient temps, and it does cut out at 3600 RPM. You ABSOLUTELY do not want your fan to be coupled at a higher speed since the centrifugal force at higher RPMs could cause some REAL damage.