Using Igus RJ4JP bearings on the y-axis for the MK3 reduces noise, but there's problems. If you tighten the U-bolts so the bearings don't slide around, the bearing deforms and makes travel difficult. So you loosen the U-bolts to where they just barely hold the bearings, but because the slot is longer than the bearings, they slide.
This piece solves that.
Print this piece (using .1mm height) and the bearings will no longer slide around. It's designed to fit tight, so if your bearings don't fit just slice off a small amount of plastic with a sharp hobby knife until the bearings fit.
The holder will bump into your tie wraps (and therefore reduce y-axis travel by a few mm on both the front and back, but my printer passes all self tests still.
I hope this helps. It's been working great for me for a couple months.