Xtx and Mtx are uncoupled so throughout the travel of front and rear of skid they don't affect each other as dramatically as the coupled 129 and 137 skids which are coupled so that at a certain point when rear is compressed the front skid shock is also compressed. This helps keep front end down for cornering and also increases the effective rate of rear shock since front skid shock is helping it. Think of it like a swaybar for the rear of skid. That is what this mechanism in pic does. I would be a little concerned whether the uncoupled skid rails will be able to handle the extra load.