[nuz69]

lincpimp, you didn't understand what i meant, here is my opinion :
Keep in mind that the motor produce the power the setup requires, the motor doesn't force its power to the setup.
Geared for the same speed, the 1518 motor will draw the same amp of his current 2200Kv 1515 setup ;) even a little less amp because it will run more efficient, and even on 4S (same power in a bigger motor which has same winding width and type).
Volt up and gear down is not always the best solution to gain some efficiency, because there is bigger amp spikes at higher voltage.
However, trying with 5S and low gearing (if the motor mount allows it) is a good idea, but don't forget to increase the punch control, in order to avoid the amp spikes which are responsible of heat and unefficiency...