We climbed Gannet the first week of September. We used 30 degree bags and were just fine. We slept on top of Bonney Pass. We used our 7mm - 30m rope and it was very helpful over and above the b'shrung. It was wide open and the snow bridge was in pieces. The nice thing about late August/early September, is we didn't see one single mosquito. The snow levels were low and we only encountered snow when we descended Bonney Pass to summit.
Good Luck!