The cables don't need a guide where they exit the fuse unless there is a possibility of them rubbing on a former as they move. Your servo arm should be the same width as the control horn. The cables should exit the fuse at a point where the width matches the servo arm/CH width. The exit slots should be long enough as to not interfere with the cables at full rudder deflection. This would be the optimum set up which may not always be possible.