Hi Walt,
That's great. Like Mike says, hold off on any dramatic nattery changes. To begin with, the EVO battery has much lower cell resistance than the 4000 mAH battery you are comparing it to. You will actually get more voltage and more watt-hours out of the same mAH draw. This is not because of different chemistry but because thinner insulator materials and better electrode plate manufacturing methods allow them to pack mnore surface area in for a given weight of the all important electrolyte. This is the direction the market is going in. The TP 4200 Pro-Lites may represent a better compromise of cell resistance and weight for Stunt. A few of us in Pattern are working on the folks at TP to create a new series of batteries with the same Pro-Lite-like tradeoff, rather than the EVO characteristic which is aimed at greater than 15C discharge. We average 7C (or less!) in Stunt, with peaks at 10C.
Most 3300 batteries aren't much lighter, so you might make your choice based on $$$.
Since you are only using ~50% of your battery capacity, you might try adding a little more prop diameter, if you have the room. That will add maneuver power and only slightly add consumption. You could up your consumption by 10% and still safely use 3300s.
Mike,
You are dropping off the governor? Are the batteries at end of life or are you just using too little pitch and a few too many RPM?
later Friends,
Dean