I think a better question is what do you want for final pop. How many plants are you ending up with  planting as you are. Many who plant above 160 thousand may do so with good reason. Drills not covering,planter problems,rougher ground,later planting. "They "say any final counts above 90 thoussand to 120 will give as good as yield as more plants. We planted 160 thousand last year with our newer planter and thought they were plenty thick.. Dropping to 150 this year.
  I would check some of last years stubble if you can and adjust from there. Maybe drop 15 to 20 thousand less and see how it goes.  Do a test plot.Only problems I see on lighter drop is making sure those you drop grow to harvest.