Bob Hoover is performing a barrel roll, which - if flown perfectly - is a 1G maneuver throughout.
As long as you are going fast enough, and pulling up enough, and can sustain at least 1g of acceleration towards the bottom of the aircraft, everything would be exactly the same. If you put a blindfold on someone, and done this, the chances are they wouldn’t even know they are upside down!
This was just an ordinary, unmodified Rockwell Commander Shrike aircraft and the entire routine was flown with both engines shut down -- trading altitude for airspeed without wasting an erg of energy. When he finished the routine he had just enough momentum to roll back to the starting point on the apron -- I doubt he even had to tap the brakes. It's an astounding display of airmanship.
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