If you use 12S LiPo and by using (2) 6S 5ah 20C Lipo Packs.
Because, 12S chargers are hard to come by. You can't find a RC LiPo charger for 12S. Most chargers are 1S to 6S.
Also safer since you are using 6S voltage versus 12S voltage - Capacity itself whther or not it is 5ah or 30ah or 60ah doesn't affect voltage or matter as far as safety wise - besides if you short the packs 60ah would last much longer but it's 6S 22.2v versus 12S 44.4v.