A hydrostatically actuable downhole piston apparatus for use in a wellbore, comprising glide spacers disposed in the primary chamber, capable of mitigating the deflection of the piston and other hydrostatic components at elevated wellbore hydrostatic pressures. The disclosed apparatus is suited for, among other applications, the hydrostatic setting of a downhole tool, such as a packer, in a wellbore. A method and system for hydrostatically setting a downhole tool using glide spacers disposed in the primary chamber of the downhole tool.