RE: Q40 servos
are there any markings left on the chip in the lead? It may be possible that the higher voltage LiFe pack burned it up. 6.6 is the nominal voltage - they start out above that, 7.2 or so.
Some may be amplified - trying to run two servos off one channel on a receiver, especially newer receivers that have lower voltage pulse outputs to begin with, may drag pulse amplitudes down far enough to cause servos not to respond.
If possible, I would use an extra channel on the receiver and mix the aileron function in the transmitter - some even have dual aileron servo functions built in.
I would be very hesitant to use a Y harness of any kind in a race plane - too many things to go wrong.