you should be installing the cover plates with two full rows on the top left side of the rotor and the rest will depend on how your rotor is loading you seive. you can install a couple under the talings return drop and the other sometimes are help full about the 6 or 7 oclock position looking fron the rear of the rotor
Try running without them first. We use cover plates the first few years. Then took them off and didn't see any difference in loss or sample quality. Capacity went up a little. Haven't used any for 3 years now. Crops we cut are malt barley, durum, spring and winter wheat.