VCarve core profiling

Hi. Im quite new to CNC world. Have somebody experience setting up profile with cnc router in VCarve soft.? So far I can import 3D model of the core I draw in sketchup. I can profile it bud struggle with the right thinckness.Im Not sure how to vertical align it in VCarve to be exact to the drawing. Always too thick or too thin. Sure there is some better way to do it.