We vary from dusting in to 1.25".  We can bank on some farms not having a stand at any depth if we get a hard rain before emergence.  Moisture is our determining factor and we have stopped planting until enough moisture left to prevent swelling with no rain in the forecast.  In 2016 we planted parts of one farm 3 times because even planting after a .6" rain the moisture never met under the surface and the trench dried out after the seed swelled.  Problem is when moisture varies 1" over the length of a field and you don't know what to do with the forecast being a guess at best.