I can't speak for the Magnum fuel....I can get 11-12 mins pretty well on the 140DZ before it barks. This is in calm conditions and a needle set on the lean side of that dead band...I have flown it 13-14 mins of just rolls and such in the last couple mins. Usually the bark or air bubble will come in on a corner specifically a outside coner or a snap.

The fuel is Cool Power 30% Heli blend.

TN