Yes, you are a bit on the "fast lane".
If my stopwatch is not fooling me, 4,8sec-4,9sec lap.
At such Speed its more difficult to fly precise , like all Loops at the same spot and angle.
Maybe try 2 feet longer lines and/or smaller venturi before experimenting with other props.
Engines sounds powerful happy on this rich 2 stroke setup.
My two Cents....gents.
Peter