I think the purpose of the curtain---the one at the rear of the combine just in front of the rear panel---is to protect that panel from flying debris and direct it into the chopper. For small grains, this is not necessary and I take mine out, but leave it in for soys and corn. My old F2 did not have this curtain, only one near the end of the raddle chain, always left it in.The metal curtain above the separator raddle must be up for corn, but lowered for soys and fully lowered for small grains----except for this year's crop of soys that were so difficult to harvest--short, green stems, weeds-- that it was basically trial and error to get them through the combine. Ben.