Since I have owned the Flatfender it has had a problem with overheating (sometimes boiling) especially on very hot days or on long steep uphill tracks. For a while I used Waterless Coolant from Liquid Intelligence. It has a boiling point of 190*C so completely cured the boiling problem but I was still concerned about frequently running in the red on the temperature gauge. I ended up buying a new Toyota FJ60 radiator and adapting it to fit. It was a lot wider at 610 mm and a very tight fit between the headlights. I had to trim off some of the flanges on it and mount the indicators further forward to squeeze it in.
Fortunately it did the job and now even on the hottest days it never goes over the green on the gauge.

Ian W.