MMP disabling the BEC

[Thomas Porfert]

That's exactly right, just pull out the middle red wire and you're good to go.

I would personally recommend using a 3 inch servo extension with the red wire disabled on the extension. Just disable the red wire on the extension and run it inline between the speed controller and receiver. This effectively disables the BEC, but when you want to use the Castle Link, you don't need to worry about putting the red wire back in or using a battery to connect to the link; just pull the speed controller off the extension, hook it to the link and make your changes, then just plug it back into the extension.

Hope this helps and let me know if you have questions about the extension setup.