When the servos die, seldom do they die in neutral. Had one aileron servo die years ago, on take off of all things. Hard over to one side, the model tried to roll of course. Hit one panel, then the prop, stopping the crate. Only slight damage....Lucky!!

I've tried dual elevator servos and decided I like my old faithful one servo with pull-pull linkages better. It is the lightest set-up yet and removes weight from the tail to boot. Ailerons are just too simple to set-up in dual servos so I do that

Redundancy is better served in the batteries/regulators imo.