Boundary with all versions of Bobcad

When working in 3d and a Planer or Advanced Planer tool path with a Boundary why is it we can not force the tool to go to the edge of the boundary. The way it is now you have to do the math to make sure your step over will come out even to the width of your boundary. I know there are other 3-D toolpaths that will stay at your Boundary but for what I do I like to use planer