We often need to provide volumes of additional excavation for substandard subgrade material to a certain depth. The easiest way to get this is through the Milling and Stripping functionality. You set the bottom of the component thickness and have the bottom follow a component, But the top can only follow the component, the surface or the highest. I would like the top of the Overlay/Stripping component to follow the lower of the pavement box bottom and the surface. This would allow us to quantify the volume that is both lower than the terrain and lower than the bottom of the pavement box.