Hello nishim, I didn't quit understand your post about the power ratio, sorry I don't know that much as far as calculating power to rotor size, battery size should be 11.1 v li-po 2100 or better mah. (Milli amp hour). The higher the mah the longer battery life for flying; you probably knew that. If I can answer any other questions fellow G2 owners let me know. Fly safe; keep it upright...!