Hi Greg,

The 25C packs weigh less than the 20C packs and so that's the main difference In regards to flying, can’t really perceive any difference. Although maybe I should mention the age of the packs is quite different, the 20C packs are just into the 50 flight mark compared to the 25C packs which might be just on the 10 flight mark . I can at least say the 'older' 20C packs are still going strong.

Your right about 4S/6S setup, the 6S can be used for other stuff like the "50e" mini-me planes . For example I use the 6S packs in a Miss Wind 50e.

Good luck with the first electric.

Cheers,
Neil
Adelaide, South Australia