[Stubby79]

I would think moving as fast as it can relative to the draw on the battery...the battery can probably only put out so many amps before the effective capacity starts dropping off. And maintaining altitude without moving (or moving slowly) is like having your car idle...a waste of fuel.

If you want to test it, you could use a watt-meter to track how many watt-hours it takes to charge it back up. You don't have to completely drain the battery in the process, as long as the distance flown and the conditions are the same each time. Chart it out in 5mph increments or however fine of an increment you are up for doing.

Your other option is to simply run it until the battery dies, at different speeds, to do the same without a watt meter. Meter would be quicker, since you don't have to go as far and don't have to go chase after where it lands when it dies.

Anything else is guessing...