Why?

What's less than an ounce of weight when you compare it to the *significant* improvement in servo-performance. Just 7/8ths fill your tank instead of filling it right to the top if you're worried about the weight.

I used to use those AAA-sized packs but found them too risky. They have too much internal resistance and if you start really throwing your plane around they can sag badly.

Now I use the 2/3A packs. Radical RC's latest 5-cell version of these is 1400mAH, weighs just 4oz and will handle up to 20A of continuous draw (that's *lots* of headroom).

I *have* flown a 4-cell AAA pack flat (it died as I was taxiing back to the pits -- no damage fortunately) despite what I thought was careful management and leaving a safety margin but I've never had any problems with the 2/3A cells.

I'd rather have a plane that weight 4lbs 8oz than one which weighed 4lbs 6oz but stopped responding half-way through a flight :-)