Battery
OK
if using BEC from ESC(s) remove the RED lead from 1 ESC. ( if not you may fry your receiver)
you may also consider 1 left hand and 1 right hand prop so you reduce torque effects.
fitting a mixer twixt throttle and rudder will allow you to get differential motor outputs as you steer.
"that's not a bug its just an undocumented creature."
Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)