Its not a draper thing, I assure you, I used to run ugly masseys, they did the same thing, 7700s did, 8820s did, my 50 with 936D does. Sealing the area between the sub frame and main frame will stop what little there is up there from falling off maybe with side channelling but my bat reel every so often will kick up a head here and there, not a rpm issue or height issue either because the reel has to be used to offer good feeding, to a certain extent. Had a customer of mine ask one time about the buildup on the feeder house and a small pile on top of the cab from filling the extensions too high of rough ground,,,, I asked him " you ever seen lint stuck to a cotton picker?" Its called mechanized harvest, it happens.