A sheets streaming and stacking apparatus comprising: (a) a Stacking Deck having a Stacking Deck Discharge End disposed downstream of an opposed Stacking Deck Entry End , the Stacking Deck Discharge End being positioned above a Load Conveyor capable of moving completed stacks downstream once completed, at least one of the Stacking Deck Discharge End and the Load Conveyor being vertically movable such that vertical distance between a Stacking Deck Discharge Surface of the Stacking Deck Discharge End and a load-receiving, Load Conveyor Surface of the Load Conveyor is variable, the Stacking Deck Discharge End being disposed over a vertical stacks accumulating region and configured to discharge sheets downwardly into the stacks accumulating region; and (b) an Accumulation Sheet Support System that is selectively interjectable into the stacks accumulating region to provide at least first, second and third Sheet Support Surfaces, the first Sheet Support Surface being defined by a downstream-wise retractable Lead Edge Support , the second Sheet Support Surface being defined by an upstream-wise retractable Trail Edge Support ; characterised by the third Sheet Support Surface being defined by an upstream-wise retractable Center Support , where the Center Support is at least selectively moveable laterally within the stacks accumulating region to provide underneath support to a bottommost sheet of a nascent stack (14"') forming in the stacks accumulating region above a completing previous stack (14") also present within the stacks accumulating region, the underneath support provided by the third Sheet Support Surface being disposed in an area between opposed leading and trailing edges of the bottommost sheet . (a) a Stacking Deck having a Stacking Deck Discharge End disposed downstream of an opposed Stacking Deck Entry End , the Stacking Deck Discharge End being positioned above a Load Conveyor capable of moving completed stacks downstream once completed, at least one of the Stacking Deck Discharge End and the Load Conveyor being vertically movable such that vertical distance between a Stacking Deck Discharge Surface of the Stacking Deck Discharge End and a load-receiving, Load Conveyor Surface of the Load Conveyor is variable, the Stacking Deck Discharge End being disposed over a vertical stacks accumulating region and configured to discharge sheets downwardly into the stacks accumulating region; and (b) an Accumulation Sheet Support System that is selectively interjectable into the stacks accumulating region to provide at least first, second and third Sheet Support Surfaces, the first Sheet Support Surface being defined by a downstream-wise retractable Lead Edge Support , the second Sheet Support Surface being defined by an upstream-wise retractable Trail Edge Support ; characterised by the third Sheet Support Surface being defined by an upstream-wise retractable Center Support , where the Center Support is at least selectively moveable laterally within the stacks accumulating region to provide underneath support to a bottommost sheet of a nascent stack (14"') forming in the stacks accumulating region above a completing previous stack (14") also present within the stacks accumulating region, the underneath support provided by the third Sheet Support Surface being disposed in an area between opposed leading and trailing edges of the bottommost sheet . <EOS>