1800 K used on road and (now very occasional) track sessions.
Standard cooling system
82°C thermostat (on the advice of RatRace)
Sender to the gauge replaced
Fan switch replaced, now 95°C
Comma G30 coolant
Runs at indicated 80°C, and fan brings it smartly back to that when needed
But cooler than that when cruising on cold days. I think about blanking off part of the radiator but I haven't got a round tuit.
Jonathan