I agree with Mr. Ramsey that under normal conditions, derailing due to unequal side forces may be rare. I had the privilege of riding a Jordan Spreader in early 1979. Part of my ride involved plowing a branch (former O&W mainline) line that hadn't seen a new tie in years. We rode to the end of the branch and plowed back towards the main line. We came to a cut on one side of the track and when the wing on that side was pulled in, one of the trucks on the spreader dropped on the ground. A track gang was called and the plow was re-railed. We lifted the wing that was still down up and got the work train out of the cut and proceeded on our way with the day's work. Tie condition does have a bearing on how well a track mounted plow can work. If the gauge is wide and tie conditions are poor, it's best to have both blades pulling equally and not taking a wide slice.