70 mm EDF. Will have a 100 amp Castle Speed Controller. I was told these have an internal BEC ? I want to be as safe as possible should I also solder in a Castle 10 amp external BEC ???
Thanks

Depends how much you value your model, I use the same speedo in my slightly larger 80mm EDF "HABU" disconnecting my internal BEC and using extra 5cell NMHi to run the receiver. Definitely advisable.

Joseph,
So do you have a regular switch like a normal setup and just have a regular 5 cell receiver pack to run your servo's ?? Also if you disconnect the internal BES I assume you done use any external BEC just the 5 cell RX pack ???
Thanks

All I did is disconnect the red wire from the ESC to the throttle channel to my RX, and use separate 6V battery to operate RX. No need for external BEC.

70mm edf, how many cells? How fast do you think it'll go? If it's 4S a CC 10A BEC is totally doable, higher power and more cells I would go with a CC BEC PRO. Always go external BEC (or receiver pack) unless it's a cheap foamie.