I know I could figure this out myself by trial and error, but hey why reinvent the wheel.
I fly in the Portland, OR area where winter temperatures rarely get below 25F and are usually in the low 40's. My SS7 has the 912ULS with the standard kit radiator and oil cooler sandwiched in front of the radiator. I do have the optional oil cooler thermostat, but no radiator thermostat.

My question is: about how much of the radiator surface should I tape off? Also should I tape off part of the oil cooler, or leave it alone because it has a thermostat?

Jim