My i6 atty just popped yesterday and I used it exclusively at 7.4 volts for
three weeks. My i6 at 6 volts has been used on my GGT for over a month now and is still going strong.
I have a lot of i7 atties Domino so if you need some in a pinch, I could probably hook you up. I'm have 6 X i7's, 4 X i6's and 4 X i3's presently. 4 of the i7's are unused. I live in Alberta.