1. Make sure you are using a switch able to handle the amps you will be pulling. A mosfet chip will help you use a normal looking switch. However, there are 60amp DC rated switches for cars and boats that would work depending on the size of your box. giggidy, but theyre big and ugly. Also, you could get creative and build your own mechanical switch.
2. If your planning on running your batteries in series, be prepared to jack up the ohms on your builds, in accordance with the voltage potential of your 'stacked batteries'. I was using a .2ohm build on a single 18650 mech mod, then put that rda on top my serial 18650 box mod, My cotton insta fried. Too much power, too little brains. I now use a .6ohm build on my box.