I run a K with a 3-30 corn head, plant with a "customized" 3 row JD 7000 planter, and spray with the same tractor on 90" centers, spraying 15 rows. I wouldn't go on some of the hills around here with 60" centers. It keeps the combine tires off the row too. I don't think you can keep the tires off the row with 4 30" rows. If I move up in size I would like to have a M2 or M3 and 5 30" rows, could keep the same sprayer and add a couple units to the planter.