JIM1

I would go for this one -

http://www.wheelspinmodels.co.uk/car...h-6-6v__1209e/

This is what I use and it fits in my Serpent with ease.

I know that higher voltage recievers are available now so using a lipo without a regulator is possible. You would also be able to take advantage of the high voltage servo's that are starting to appear. I don't know anyone who is using them yet though. I am very 'pro' Futaba for radio's and I'm sure they don't make a high voltage reciever yet, so a 6.6v life for me is a better option than using lipo.