On the subject of the backwards battery placement, it's really not a good idea. As was mentioned by someone else, the body of the battery is negative. With the battery in place positive side up, the body of the mod is the negative as well. If there is any sort of tear in the battery's wrapping, and it touches the wall of the mod, it won't be a big deal. It will simply complete the circuit (bypassing the switch) and power the coil just like you are pressing the button.
If you have the battery reversed, the body of the PV becomes positive, but the body of the battery is still negative. If there is a tear in the wrapping, and it touches the wall of the mod, you will have a hard short. It will connect the negative body of the battery, to the positive body of the PV. This will be far worse than the previous scenario.
Before a tear just resulted in bypassing the switch, this time a tear results in hard shorting the battery. Because the short is directly between the wall of the mod, and the body of the battery, there is nothing else to stop or break the circuit. Unless you catch this almost instantly you'll overheat and vent your battery.
We're all adults here and I'm not trying to tell anyone what to do, but it's a really bad idea to put the battery in backwards.
Just to clarify, we were discussing bottom button devices. All bottom button mods that I am familiar with isolate the bottom of the battery and when depressed, make contact completing the circuit. There is an unbroken connection from the top + end of the battery to the switch housing. The bottom of the battery is typically isolated by a delrin washer or o-ring. These are the devices which, IMO, should be "upside down".