A volume-adjustable unit including a first layer, a second layer, and multiple inner paper layers disposed between the first and second layers. To increase the torque tolerance of the screw and to minimize the likelihood of the driver stripping inside the bore of the screw, the screw and driver are heat treated together to shrink fit the screw onto the driver thereby increasing the driver-to-screw contact and distributing the loading force over a greater area to protect against material failure. The method also includes forming isolation structures between adjacent fins; and forming doping sidewall spacers in top portions of the isolation structures near the fins. In one example form, a plurality of closely spaced idlers is also provided to support the belt adjacent or near the weigh frame in the transition regions.