ST43 pads are the culprit here given all the other variables. They put out a lot of heat.
Unless youre chasing that last tenth under braking and dont mind rebuilding your calipers often: simply switch back to stock Ferodos and your issue will be fixed.
Stock Ferodos have much lower torque and are gentle heat wise even under hard and extended use regardless of track venue layout.
I use them and think they are well matched to the tires and cooling parms of a stock car. The only disadvantage is they wont last as long as ST43s. But there is never a free lunch
