When installing flap servos, you have to make a choice. 

If they will be on separate channels, then you install them so that they are mounted opposite each other. This makes for more uniform motion.  That is the way yours are mounted.

If you are going to Y them then you face them in the same direction so they move in the same direction.

If you have them mounted so they are in opposite directions and you decide to Y them then you need a reversing Y cable.
http://www3.towerhobbies.com/cgi-bin...XAFN1&P=ML
or
http://www3.towerhobbies.com/cgi-bin...XAFN2&P=ML