Can someone explain the Five Volt Sweet Spot to me? It seems to be the ideal voltage to vape at (I've seen it used for the Prodigy). But the Prodigy is 6 volts. How do you get it to run at 5 volts? Alternate batteries or is there a separate mod for this? Or is there a setting on the Prodigy itself. I ask because I'm considering buying one. Thanks.