‘The Mustang was well named, for it could be a wild beast if you did not know its ways.’ So said Richard Burns, a WWII fighter pilot of wide experience in other single engine fighters. ‘A lot of men got killed finding out. I have heard it described as an unforgiving aeroplane. It was no more unforgiving than any other aeroplane where the pilot did not know its limitations or ignored them. It had a lot of power and very clean lines and would quickly go wild on you if you didn’t keep a tight rein. I don’t think I would have liked to go straight from an AT-6 to a Mustang as some guys did. It was a big step unless you were cautioned what could happen. Apart from that the Mustang had good aerobatic qualities and with the light control pressures was a joy to stunt around.’
If I recall correctly the Don Busch finding was the influence on the handling with the amount of fuel he had in the fuselage tank (located behind the cockpit) and his lack of experience. This tank had a capacity of 85 US gallons. With the tank full the C of G is so far aft it is almost impossible to trim for hands off level flight. The stick force per G is reduced from 6 to 1˝ pounds and in a tight turn or if pulling G the stick forces reverse. The flight manual cautions pilots to exercise care if the tank contains more than 25 gallons, and if the tank contains more than 40 gallons aerobatics should not be attempted as the aircraft is unstable for anything but straight and level flight. With the tank more than half full a series of stick reversals occur just above the stall and the stall occurs with sharp wing drop and no warning buffet. Unless immediate recovery action is taken a spin is likely to develop. Recovery from a spin is recommended to be complete prior to 10,000 feet. Some pilot notes describe the power on stall as ‘violent.’