if you want some extra run time get a hump and a flat reciever packs. you can put the hump pack under the gas tank and the flat pack on the underside of the chassis. make sure they are the same milliamps and run them paralelle.

For me i just went with the bigger gas tank. and a 1600mah flat reciever pack. thats enough to go for a while tell i get bored. i have jr z590m throttle/brake servo jr z270 forward/reverse servo and 2 jr sport st126mg for steering.

also remember the more powerfull the servo= the more juice it will use