actually with my 1050 li-po i get about 10 more flight than what you will with your 1650 ni-mh packs!!! in my imac plane i was using a 1700 mah ni-mh pack and only got about 5 to maybe 6 flight before needing a charge, when i changed over to a 1550 mah 2 cell li-po i was abot to get about 15 flights before i needed a charge!!! you have to remeember a 2 cell li-po pack is 7.4 volt and 8.4 full charged!!! where a 4 cell ni-mh pack is only 5.5 full charged. that almost 3 more volts!!! even though the regulator is only giving it 5.4 it still has to work it's way down til it's close to 5.4 and plus 2 cell pack you can let get down to 5.1 volts before you need to charge it!!! thats why on li-po's you can get more flights even with less mah's, really all the mah's mean is how many amps and power it's going to give.
i an my motor today since i have never had this motor imverted, i used a tip i read on here about getting the tank cg even with the carbs spray bar and it works great, it ran like a champ inverted!!! and it has tons of power at full throttle it wanted to rip ot out of my hands holding it straight up. plus guys you have to remember i'm running 30% comp. heli fuel and 14x4w apc prop!!!!
you should try a li-po in one of you plane, just pick up a 5.4 or 5.1 volt regultor and a 2 cell 1050 or 1200 mah pack and you will see the diffrence after 10 flights and you can still keep flying!!!!


mike