I flew in the rough air so it was not that it was a temperature and fuel shortage. My 75 burns 8 oz in a flight and that the size tank I have. When its cold or cool it need s 1/2 oz more or it will run out on 4 leaf. I had no 5% only 10. No excuses only regret.
All you needed was to have a gal of 5 and a gallon of 10%, that way you can use either 5, 10 or make 7.5%. I have all my guys do this, once you fly with the different Niitros you will get a good feel what you need, and if you had just dropped to 7.5% , you would have had flight time and the engine would have been close to the exact same power.
This is a simple thing to do, and is much much easier than removing the head and adding shims, or guessing on venturie size.