You don't need a reversing "Y'. What it does is when two servo's are
hooked together....(y-ed)....one servo works in one direction, and the
other one in the other direction.

That's what it says in the directions, if you want the servos mounted
with the arms sticking out to the sides, like pictured in the instructions,
you will need to use the reversing "Y".

However you can mount the servo arms this way, and save the expence
of the reversing "Y" wire connecter. Mount the flap linkage straigt, like this....
instead of to the side. I have done this on 3 Ultras....it works fine.

You will still need a regular "Y" connector to hook the flap servos
together.

Dave.