My clone B6 has behaved impeccably for years. I can get a whole day out of a 1000mAh LiPo no worries with the gun set to single shot burst.
Stick with 7.4s.
I use 1500s for most games, the cheapest on Evilbay.
I tend to charge everything in a lipo bag, in my line of sight.
Standard NiMhs are shite in comparison.