as long as they can handle the current. (about 20 amps), you should be fine with your li-pos. you may need bigger pinions though, but probably not since it is so light. as far as safety is concerned, if they were matched closely, you will not have problem with one draining before other. we parallel pack the cells all the time. the key is not to drain them below 3v per cell and balancing them out once in a while to make sure that we don't over charge them. i don't hink diode is going to help.