we get 5ish minutes on a 3s 650mAh lipo, but conservative flying might get you more (I have the timer set fairly conservative as I don't have battery voltage monitoring on them - I have another craft with the same motor/batter/prop which I get 8 minutes on). Where I would look at, is to see if on 2s you would have low enough power draw to run a 2s 3000mAh li-ion pack, which would get you ~4-5x the battery life I was getting on my lipo... which means 20-25 minutes... (maybe a touch more).
Based on the flight times I get on the 3s, it looks like my expected average draw would be around 4.5A (A pack w/ 6x3 prop).
I would bench test as the 'high drain' li-ions are rated for around 10A, but based on above, your likely ok
70% of the 3Ah of the li-ion gives this at 5A -> 2.1 Ah / 5A = 0.42h => ~25 minutes.
however you have 2 other issues:
- radio link (Rotor riot did a very non-scientific test and standard 2.4GHz links were getting around 2k feet or 3/8 mile - this was near the ground and on a quad, so I suspect in the air you will get better)
- LOS rules in many countries. (at the air field I fly at, the 'edges' are around 600ft from the flight line and I wouldn't go much farther then then that with my TT for orientation stuff - given how distance works, maybe 2x that, but at some point, which I would expect well before 1/2 mile to not be able to qualify this)
