it suited my installation to have then flat against the wing to prevent fouling anything in the fuselage and it makes connection easy.
3 pins for ail servo
3 for Flap servo
2 for U/C signal and common - power from on wing battery. - in your case case signal and common from ESC if you are using Rx battery
However - There is a device to allow sharing dual esc power to RX but not cheap
www.jetimodel.com/katalog/dsm-esc-dual-switch-mixer.htm