You make a 2D tool path , I use the boundary , make sure it iis a seperate layer and directly over the surface you want to machine. It will then follow that path only on the surface . This is better than projecting a curve since it will prevent your tool from gouging the surface on sloaps,ect . As far as making the tool path you can use a backplot from the toolpath section . Or if like me you also have Mill Pro 2000 ( maybe even Bobcad ) you can draw manual tool paths and import them into XP. I have been in touch with the man downunder and he says version 5.20 will add more of these older features for use with this funtion. If you do alot of surface cutting you'll end up loving this function .