which model flex fan did you get.do you have the nismo thermostat installed as well.

 

The biggest problem with rads is that they decline in efficiency with each year of use: bent fins, dirt, oxidation of aluminun on outside reducing transfer etc.
The decline is so slow it is missed until stressed.
Same problems with electric fans, as they age the slow down and down and down.

Adding more coolant capacity is often more useful. A few extra quarts can do wonders.