For those of you that are concerned about the effects of a fuel cooler in cold northern winter temps, I think I might have a DIY automatic solution.
Looking at
www.haydenauto.com , they sell 4 different types of thermostat controllers to go along with the electric fans they market. One of them is nothing more that a simple on/off thermostat with a temperature probe, adjustable from 32 F up to nearly 200 F. Advance Auto carries this same thermostat under the Imperial name for around $35.
Also, I remember from my years of idly browsing JC Whitney and other parts catalogs, that they make electrically operated fuel tank selector valves, for pickups and larger trucks that have more than one permanently installed fuel tank, such that the driver can switch fuel tanks from inside the cab while driving. Pollak is one brand name I remember.
Here's the idea - with the fuel cooler installed in the return line, install one of the fuel tank selector valves in the incoming line to the cooler. Plumb the selector valve such that when deenergized it directs flow around the cooler and back to the tank - allowing hot return fuel to warm up the tank-, and when energized directs flow thru the cooler before returning to the tank - cooling the return fuel and preventing the tank from being warmed up any further once it's at or above the desired temp.
Install the Hayden thermostat so that the temp probe is tystrapped to the supply line to the filter and injection pump. The temp of the fuel going thru the supply line should be at or close to the temp of the fuel in the tank itself. Wire the thermostat such that when it exceeds the set temp, it activates the fuel selector valve and directs return fuel from the engine thru the fuel cooler. Adjust the temp setting of the thermostat to whatever temperature suits you.
During the winter you'll have hot return fuel from the engine warming up the fuel tank along with the electric heater in the filter in the supply to the engine, and during the summer you'll have the fuel cooler removing unwanted heat from the return fuel before it goes back to the tank, all operating automatically.