I came up with a way of making the sliding elements for my X axis on my XY laser.
I used ball bearings instead of the plastic channel.
Each sliding element is powered by a belt (like the XY Plotter). Each sliding element has 4 bearings. Three to ride the angle frame and one for lateral stability. The three that ride the frame are two above and one below with an adjustable spacing.
It seems to work really well.
After I mount the pulleys, shafts and belts, I'll report back.