Good write up,im not sure were it went wrong with the engine heat? At the british event at castle coombe 17 of us were averaging 5.5mpg in 20 minute sessions for 6 sessions and not one overheated,the day time temp was about 22/23 so probably not as hot as where you are.From what i can remember we were at full chat from 3500 to 8500 because of the torque.Im probably wrong,but could it be that if you were running at 6000 and above all the time that was the problem and did you need to run that higher rpm.One thing i remember that the 12c develpoment drivers who were our instructors told us to do was to short shift between some corners as it had the grunt and didnt need the revs all the time!!