It's hard to say precisely because with a regulated mod, it's gong to depend on what wattage you want/need to use. Lower resistance and higher mass builds will require more wattage (usually) to get a satisfactory vape, and whether a single battery, even a highly rated one, will be able to give you the performance you need without overstressing the battery.
If you want a dual coil build, I think you may be correct in believing you may do better with a dual battery mod. I would maybe try the single coil with your LG battery and see how you like the vape (I'm assuming that you'd double the resistance and halve the mass with the single coil) and what your wattage needs are. That should tell you whether or not you are going to need to use a two battery mod.
I'm not a huge fan of redlining mods or batteries, so if in doubt, I usually urge erring on the side of caution. If everything's great and you get fantastic battery life, maybe your dual build will work. I'm a bit doubtful, but everyone's build "sweet spot" is slightly different and etc.
Anna