I purchased a Dubro pull pull pack and used the "wedge" site as a reference.

http://www2.towerhobbies.com/cgi-bin...?&I=LXD858&P=7

I setup the servo and control horn so that the lines ran parallel, and put the control horn (pair) just *slightly* back from the hinge line to introduce some "Ackerman effect" and it work out fine. At full rudder deflection the non-pulling side goes slightly slack as expected. At center, both lines are tight.