the problem comes not from the voltage but from the mah of the batt. with lr you really need above i think 500 mah to run lr.
the reason is it stresses the batt past its saftey zone. without getting into to much tecnical talk and jargon basically
it might work for a while and thats fine but it will kill them very quickly if not cause other complications to arise.
with egos its not the mah but the mosfet switch. it cant handle that type of drain. it will kill the switch at some point.
now if you really want to use the dual
coils Madvapes sells a cheap 3.7v
mod.
called the roughstack v2
RoughStack V2
batteries :
Protected 18350 Lithium Ion Battery (recomended buying 2)
for the price of about 50ish bucks you can have a 510 connection super small 3.7v mod that has 1200mah and will allow you to use the dual coils safely
but thats my 2 cents