I have noticed little difference between 60% and 100% rad when it comes to oil temp. With either engine doesn’t overheat, only oil does and only way to stop it is to lower engine output by a good 5% through prop pitch (depending on alt, at 5000 the performance drop is so hige, you can use 100% without overheating).
LF Mk IX at low alt requires either removing huge part of engine power or 100% radiator. So it’s indeed tricky, you have to constantly adjust either for lower speed acceleration and climb, or for speed. Still easier than german prop pitch adjustment :P
Gaijin is probably not lowering air temp at alt because thay would actually encourage people to fight at higher alt more. And this game is so broken, there’s 0 reason for typical player (a.malicious troll) to come back down.