I quite happily use an 8/15A switched mode BEC for the radio and a 5A switched mode for the ignition. Both are connected to the single 2600mAH 7.4V Lipo. There is only one battery in the plane.
This is on 35MHZ (Corona), CRRC Pro 26cc rear carb and 70" Yak 54 with 6 digital servos.
If the radio and aerial are installed with the usual care, there is no problem. Knife edge loops head-on with the aerial pointed at the plane.....
As for the best? sorry, never tried it!
