Another way to get rid of a lot of dust and dirt is to get one of these perforated feeder house btms, new or exchange the core. They have a special shape perforation and overall size that has been tested and that drops a lot more dirt than the round hole. Drops around 150 pounds of dirt an acre in beans. They are available at Grand Forks Eqpt, Grand Forks ND, or at loewen.