I see a couple of misconceptions in some of the above comments. First off, you are better off with some positive Ackerman in any pull-pull system and that means that the line not being pulled will slacken off a slight bit as a control surface is moved away from neutral position. The second one is that the length from the hinge line to the attach points on the horns must be the same as that on the servo arms. In fact, you can have the horn lengths as long as you want with no problems other than reduced sensitivity. There is a limit to how short they can be though.
as long as when the servo is at full deflection, the moveable surface is not moved beyong the limits of the hinge line, you are perfectly safe. Another popular misconception is that the run from the servo to the horns must be perfectly straight. Not at all true, if you use the proper guides you can turn them 90 degrees, route them around obstructions or most any other shape. Real planes have been doing this for ages with no problems and I have at least 10 large scale planes that I route cables around structure with no problems. Once you do a few pull-pull systems, you will never use push rods for the bigger planes or where minimum control slop is allowed. Probably the biggest mistake I see in most pull-pull systems is to tight a tension on the lines. You want just enough to prevent any slack in the neutral position.