iirc, the oem as delivered, is relieved by grooves on the edges, so I don't think a replacement is immediatly needed, if the wear in the middle is not excessive, I think you are good to go.. might want to question SISF about this, as he has disassembled numerous ZG engines, and seen a few more sliders than myself.
he might be able to assist, also REVRIDER might have some input, as he has pulled his apart many times.. and prolly very familiar with the slider.