My next door neighbor had their fence replaced recently. The new fence is further from the property line than the old fence was, so I have either 5 or 6 holes where the old posts were located. I am going to fill these holes with gravel and then add dirt/topsoil and some grass patch quick fix. Is there a recommended amount of topsoil to put down on top of the gravel? I know I will have settling with the gravel fill, so the grass will wait until next year.