I’ve been making this way too hard. I am going to cull the best ideas from this thread and fix this.
Decided to forget about the bottom 1/8” and just use the 1/2” x 3/8” bar stock I bought. It’s nearly flush with the surface and has very little play (about .013” or less than 0.8 degrees across a 16” sled).
I drilled oversized wood screw holes and will screw the tracks to the bottom of the sled.
If I shim the track from opposite sides of each track, that should limit the play.
Using #8×3/4 wood screws.
-- Doug - When all you own is a hammer, everything looks like a nail.