In addition...................There is an inherent risk in stacking
batteries for any high drain use. I'm most familiar with flashlights and PVs. In PVs I've moved to using only LiFePO4, for stacking, as they are the safest and if there is a problem they only exhaust oxygen and no risk of fire. Even though protected
batteries are "protected" that protection does not protect against explosions, fire, and release of potentially hazardousness chemicals.
My short protected lithium batteries are now used only in singles in shortie PVs such as the shorty Roughstack, Super Mini GLV, and Shorty Megalodon and my head lamps that take short, single, li-ion. I'm even thinking about moving to LiFePO4 for head lamps as they are so close to my eyes. (I use them all the time working outside at night. They come in really handy when we lose power at night for just moving around the house and reading.)
Alice