Here is an example of how we are having to do it now, maybe this helps determine an easy solution, to where the LS can do the math for us.
In the clouded area, there are 3 basic points, PT#2029 is the centerline station @ 16+75, PT#1029.1 is the hinge point for the 4:1 slope, and PT#1029 is located at 90 degrees to the centerline at some arbitrary distance, in this example we used 100' from the centerline, notice the description of 16+75R100. There is a 4th point but its a projection from the radius and is part of the Line for Station 17+75, ignore this point for this example. If you notice the other side of the line has PT#2029.1 and PT#3029, which is the other side of the roadway slope. Same procedure on the other side.
We tell the LS to stake a line between PT#1029.1 and 1029, since both elevations are the same, the cut/fill is computed level between the two points, and as the cut/fill meets the 4:1 slope we can determine the catch point. We have to calculate the catch point by hand. Its great that the LS will stake a line and stake the percentage along the line, but in this instance, that will skew your results. So make sure the points are both at the hinge point elevation.
If the LS could give us an in, out along the line based on the slope and cut/fill, that would simply things.