In this project I am using a miter gauge that did not come with the saw so its manufacturing tolerances were not controlled by RIDGID. Given that, I think I probably am removing some metal from the slot. To do that I used a Dremel with a bit that had sandpaper. I did see sparks so I know I removed some metal. I could have sanded the bar on the gauge but then it might have become sloppy in the right slot.
One other thing I think I see is that the bar of the miter gauge seems to be hugging the the right side of the slot on both right and left. I can't see any high spots so it might be that the two sides are not parallel over their heights.
At any rate I'm getting there and getting new appreciation for a "Thousandth or two"