Disclaimer, I am not saying anyone else should try this, and hold no responsibility if anyone does and stuff goes boom 
The way I duck down my voltage is fairly crude myself. I have a puresmoker v2 unit, I just took the switch disk that bumps the voltage down from two 3.7v cr batts to ~ 5 volt and place it on top of the positive terminal on the top battery when stacked in the GG. The disk sits a bit higher than the terminal top, so the voltage passes through the disc and I get that ~ 5v vape from those batts. I havent noticed a problem with it or batt issues.
My own concern had been if the disk would heat and damage the top of the battery but this doesnt seem to happen or hasnt yet anyway (couple weeks trying it on and off).
The way I duck down my voltage is fairly crude myself. I have a puresmoker v2 unit, I just took the switch disk that bumps the voltage down from two 3.7v cr batts to ~ 5 volt and place it on top of the positive terminal on the top battery when stacked in the GG. The disk sits a bit higher than the terminal top, so the voltage passes through the disc and I get that ~ 5v vape from those batts. I havent noticed a problem with it or batt issues.
My own concern had been if the disk would heat and damage the top of the battery but this doesnt seem to happen or hasnt yet anyway (couple weeks trying it on and off).