Capacity has nothing to do with why I won't use these batteries in a higher load situation. I have 2 of these packs with Sanyo cells , a 1100mah and a 1650 mah. When I load test them the voltage will drop to @4V with a 1 amp load (4 cells). If you have a digital servo bind up in flight it will put more than a 1 amp load on the battery. This will not be good.
If you have a 5 cell pack you could live with the voltage drop because the battery won't drop to the point that the receiver quits.