I have been stacking batts for 3yrs. Blewt said it best, the minute we say go for it shit will hit the fan, LOL. Respect the batts and use some common sense and you should be fine. Once in 3yrs I had a set get hot on me, I unscrewed the PV and got away from it until they cooled off. I can't remember what the deal was but it was my fault, I think I over discharged them, bad dawnie. Up until that time I was not keeping them in pairs, or paying any attention to how hard I was using them. Live and learn, now I mark them in pairs, rotate 3 sets at a time and take better care of them over all. No problems. Good Luck.
"The ecig community is filled with some of the strangest mother fuckers Ive ever encountered on the net. I can't even begin to guess why." Nuck