Excellent. Thanks for the tips. I ordered one extra battery so far. From the reviews I have got it seems to be that I should be able to get 8-10 minutes out of the battery.
So if I were to find a 2100mAh battery with 35C rather than a 20C discharge it would last longer? As well as going from a 3 cell to a 4 cell would make more of a difference than a higher mAh rating.
I understand the effects it may have on the airplane. I may keep it as is and fiddle with batteries when I have more experience with it.