This is JohnSL's Y-Axis Sag Fix with the following changes:
I added about 1/8" of material around all edges to make it stronger so that it would not break when you remove it from the built plate.
I reduced the radius of the clearance cut for the steel rods to increase strength.
I added some fillets for looks.
I include Solidworks files so that you can modify it.
- Made the STL files compatible with Slic3r.
I recommend that you build it with support with the bearing channel facing downward. I used honeycomb support in Slic3r with 5mm spacing, and 5mm spacing on a 1-layer thick interface layer. The support removed very easily.