Well, I used to run the front set of straight bars all the time, and then install the rear set only for corn. They are not hard to change, you only have to remove a couple grates to get at them. We only harvested soybeans, and got along fine leaving the front set on. goalie is right, you can make a decent job with just cover plates on the large wires, but I always ran the small wire concaves to do the best job I could. What seives do you have in you're machine? If you have the longer finger corn shoe, I would switch it out for a 1 1/8" grain shoe, and you will be able to do a much better job in grain. I left it in for beans and corn, but always ran it pretty much wide open for corn.