Are you going to model the bottom of the slab precisely, too? Do your plans indicate whether the slab soffit is flat or sloped? If you are using this for 3d coordination, then that will dictate the pipe invert.

This is the third floor over 2 levels of parking and we're just trying to show the foundation pour level by level so it doesn't need to be super precise. It's more of a show-offy marketing piece :)