One thing to be aware of: you need to build in something called "positive Ackerman" to ensure the cable goes slack on the non-pulling side as the rudder moves away from center. It doesn't matter whether you use cables or rods...

See here: http://members.cox.net/bdfelice/Pull-pull/pull-pull.htm

If you are sloppy and build in some negative Ackerman then the geometry will be such that the non pulling side of the cable pair will tighten as the rudder rotates away from center. Since it is hard to build it perfectly neutral, a good way avoid to problems it is to intentionally add a bit of positive.