Right, slack is better than getting tighter. If the attach point on the horn is aft of the hinge point, that is positive Ackerman (where the non pulled line get a bit of slack as you move off neutral). If in front of the hinge point, the line not being pulled will get tighter as you move away from neutral. Depending on how much offset is present, this can cause the servo to be overloaded and will certainly result in high servo current being drawn