I came accross this website which allows you to configure graphically how to wire up lipo batteries. I have some 1S lipo batteries 180mah weigh 10.9g each. i have a 350mah lipo 2S batery which weighs 21.1g.

thinking to save weight, either buy some new lipo’s or use 2 1s Lipos which can be fitted flatter and wire them up according to this site:

http://scriptasylum.com/rc_speed/lipo.html