I have the Indulgence, to use 6v you need to order the 6v sleeve/cup (out of stock atm) The 6v cup comes with 2x 3volt batts, and apparently the charger you get with the Indulgence starter kit can charge them.
So Get the Indulgence, put the 2x 3v batts in the 6v cup, select a thread cap to suit your HV atty of choice, screw together and
vape!
So to do this you need:
*1x Indulgence starter kit (contains charger and 2x 3.7v batts, standard cup [will only fit one batt at a time], threadcaps etc.)
*1x 6 Volt Cup (contains 2x 3v batts)
*High volt attys of choice.
BTW:
The 3.7v EXTENDED cup is the same size as the 6v cup but it comes with an 18650 battery not the 2x 3v ones.