Hi!
Personally I would never use a Y-coupling!
It is much easier (safer, stronger, lighter) to couple the elevator haves together with an Easton aluminum arrow shaft tubing and use a single (Easton) arrow shaft as pushrod. These arrow shafts are lighter than carbon fiber and just as stiff.
If possible I always use a pull-pull wire system (thinnest fishing wire). Lightest and stiffest method to control elevator and side rudder.

Regards!
Jan K
Sweden