RE: 11.1 v li-po 20c safe to use with a 25 amp ESC?
The C rating of the battery has nothing to do with the esc's ratings. If you plane came with a 12C pack you'll be better off with the 20C pack . The motor will not strain the pack. I'm guessing if the plane came with a 12C pack that it's not a high drain system anyways. As long as your motor and esc can handle 11.1 volts your fine.