I used stacked 18350s in my VAMO every day. I don't need the extra power but, they seem to last longer and until the replacement spring from Health Cabin shows, up the bottom doesn't heat up like it does when using the 18650 battery. I think that's because the spring is compressed enough that the resistance is negligible when using 2 18350s and not when using a single 18650. Doesn't really get hot with the18650 but when chain vaping it gets quite warm. If you need a new spring and got your VAMO (Bamboo) from Health Cabin just go to the support area on the web site and start a "ticket" giving your information and the order number of the original order for the VAMO and they will send you a new one via Chinese snail mail. 20 to 30 days to get it.