I have built a lot of sleds with different runners. I now use the Incra miter Sliders. They are more expensive but work great and you can adjust the fit to your miter slots. When I am done with the sled, I take the bars off and use them on another sled.
With my saw and the miter sliders, I only use one of the slider bars.
Note: sorry about the strange wording but spell check/autocorrect got me and I failed to see it.