Good thought, but I hi-lited the part where u went wrong. Ur thinking along the right path, but there is another way to make the loop "appear" round which u forgot: What we actually do is ease off of the elevator and spend MORE TIME in that portion of the loop than in the bottom portion. It's impractical to suddenly accel 20 kts at the top and fly over the top in the same amount of time (and many a/c don't have the power), so we fly that portion at the lower speed,pull less, and take longer.