A headbox (10) for delivering stock (11) to a forming surface in a papermaking machine with the headbox (10) having a slice chamber and a slice opening (16) and having trailing elements (18,19) positioned in the slice chamber extending transversely of the headbox with means anchoring the elements (18,19) only at their upstream ends with the donwstream portion unattached and constructed to be selfpositionable so as to be solely responsive to forces exerted thereon by the stock flowing toward the slice with the elements (18,19) having greater structural stiffness in the cross-machine direction so that the elements (18,19) offer resistance to deflection in a cross-machine direction by transient pressure variations and offer minimal resistance to deformation of the fluid flow stream for balancing forces on opposite sides of the elements (18,19) with the elements (18,19) in one form being laminated with a plurality of anisotropic layers.