I fly another machine on 12s with Rail 556mm mains and a Pyro 650-62. AUW is 3.1Kg with 12s 2700mAh (860g). I've also tried 3000mAh (940g) and 3300mAh (1000g). I'd say it flies best with the 2700's. The 3000's are OK but with the 3300's it really feels like its losing hang time.
Do we know what the weight of the E5 airframe is yet?