6 cell question!!
 

I am thinking about doing the 6 cell mod and I was wondering do I need to do anything first to make it safe. Do I have to switch to a new fet or anything like that??

If you're doing 6 rechargable 1.2X volt cells (6 x 1.2 =7.2v), then you're safe. You won't have to worry about any damage to your Xmod. There is a circut breaker in place in an Xmod. If you exceed 8.4v, the preaker will trip it self and you'll think the car died. Let it sit for about 2 minutes (for the breaker to reset) and you'll be up and running again. On the other hand, if you go for something like 9v +, you'll override the breaker all together and your Xmod will tun into a $50 paperweight.

Maybe a more important question would be "If I'm using 6 cells that weigh 14grams a piece (84g total) just to get 7.2 volts, will the additional voltage offset the weight for long, and what other battery alternatives are available".

mine handles 9volts fine i just use almost dead batts and push the wires on to the propper side of the batterie so it looks real ghetto but works

A dead 9v batt isn't 9 volts. Probably closer to low 7s. Not 9.

i use a new alkalin 9v but dead aaa batts get it so pretty much only 9v is goin through the hole car

I'd like to see that one.