Thanks guys,
from my experience so far, I expect the CC BEC Pro can co-exist with a Scorpion Backup Guard.
But there are questions out there.
I've pretty much decided to simplify my system, ditch the BEC and backup guard, then load up with a 2S lipo to run the control system.
I'm thinking to mount the lipo under the ESC (where the BEC currently lives) and decide whether to mount a switch to save unplugging the battery between flights.
I'll get onto it when the Christmas festivities are done.