What everyone else said about the reversing part, the reversing Ys are bad news.
Depending on which servos you have, It may be easy to reverse them yourself and not need the reversing Y.

As for the rest of the question, The Y should be as close to the RX as possible and run two long servo leads.

Have you looked into systems that can combine retract and brake to a single channel to free up a channel to allow the mixed elevator function?