Abstract: A combine harvester includes a feederhouse configured to convey a crop material from a harvesting header, a threshing system configured to receive the crop material from the feederhouse and separate straw therefrom, and a cleaning system below the threshing system and configured to separate grain from chaff of the crop material. The cleaning system includes a stratification pan, a chaffer, and a blower to direct air rearward and upward through the chaffer. The stratification pan has a frame, a series of adjustable ripple members coupled to the frame, a series of support members pivotally coupled to the frame, and an adjusting rod configured to move the support members to change an incline angle of the ripple members relative to the frame. Each support member also supports one of the ripple members. Related methods are also disclosed.