Let's use your Electra as an example:
For the Electra, the voltage of the LiPoly is perfect. Problem is, the Electra's motor draws 25-30 Amps at full throttle. If you check the documentation/advertising/labeling for that 1200mAh LiPoly pack, you'll see a "C" rating. That tells you how many Amps the pack can draw as a multiple of its capacity (C is for capacity, thats good enough for me, oh capacity capacity capacity start with C!!!!!
). Okay, enough channeling Cookie Monster...
Anyway, the pack will be rated at something like 10C, for example. To figure out how many Amps the pack can handle, multiply the capacity of the pack times its C rating. 1200mAh times 10C is 12000mA, or 12 Amps.
We have a motor/prop setup that draws 25-30 Amps, and a pack that can only handle 12 Amps. You can probably guess already that it's not going to work.