If you change from a MAS 15x8 to a MAS 15x10 , both K series (if they exist) RPM should decrease about 1000 RPM. If you want more pitch at about 9000 RPM, a 14x10 should run at about 9200. I don't know what the MAS to APC change will do. I think it won't get the 1000 rpm back.