What temps were you getting and where from.
Cossie rad switches tend to switch in way too early and stay on way too long especially when fitted with aftermarket alloy rads, mine was the same.
MSD sell a new thermos switch that switches in at 92C and off at 88C, which is much better, 4C is a normal sort of cycle amount, the std one cycles from 88C to 79C, so that is why it is on a long time.
tabetha