Not knowing any better from the start of my vaping career I was stacking batts in 5v boxes mods from the get go. I still do BTW. Now that I do know better your local B&M is, IMO, full of poop. At least in the case of the Vamo, it has enough protection in it that it's not a problem. The reason I run stacked batts in the Vamo is because I was silly enough to buy some 2.5ohm DC cartos. They need the power of stacked batts to give a good vape. When running a single coil I just use an 18650.