Leo good news. I just got this one delivered for the servo upgrade. http://www.aliexpress.com/item/GTBracing-LOSI-5IVET-Carbon-dual-servos-large-battery-compartment-bracket-LOSI-052-GTB-racing-losi-5ive/32634636772.html
Looks brilliant and quality. The battery box is 140mm long and 75mm wide and the height is 35mm. In this you have freedom to fit just about any battery you want and have free space for other components like lights or kill switch so you don't have to cramp anything in your receiver box. I'm glad I didn't go with expensive alloy one as they are heavy and the battery box has been claimed to heat up under the exhaust acting like an oven.
So one of these will fit without flat plugs.
http://www.crazyhobbies.com.au/electronics/lipo-batteries/n-vision/lipo/7-4v/nvision-pro-lipo-8000mah-90c-7-4v-tubes.html