A surgical instrument for being endoscopically or laparoscopically inserted into a surgical site for simultaneous stapling and severing of tissue includes force adjusted spacing between an upper jaw (anvil) and a lower jaw (staple cartridge engaged to an elongate staple channel) so that the height of staple formation corresponds to the thickness of the tissue, yet does not exceed the height range that may be accommodated by the length of the staples. In particular, collapsible staple drivers may be supported within the cartridge for driving a staple or staples supported thereon into forming contact with an underside of an anvil attached to the instrument. As the staples contact the anvil, the drivers can compress or collapse to control the overall formed height of the staple or staples based upon the amount of compression forces experienced by the drivers during the stapling process.