Geez why not keep it simple go with a NiCad 700 mAh. You can get 4 or 5 flights out of that but after your thrid flight monitor battery voltage and you consider the battery fully discharged at 1.1V a cell or 4.4V on a 4.8v a pack.
I like LiIon batteries but they require a good charger and a voltage regulator in your plane. Takes forever to charge but you only charge every 2 to 3 weeks.
again you must monitor battery voltage and charge at 7.1 V a pack