A version of the sled which leaves in the center part to help with router alignment
This version of the sled leaves the middle puck in place and adds a center hole which can be used to help align the router on the sled.
The original credit for this idea goes to Stephen_Slagle who proposed the idea.
The CAD file for this project can be found here: OnShape
The download includes DXF and SVG files for the design, the MakerCAM project file if you just need to tweak the router bit size or such, and ready to run Gcode for a 1/4 inch router bit. Note that tabs are not saved from MakerCAM so you will need to re-add the tabs.
A photo of the back side (ignore the extra cuts, this was made from the backerboard of my original machine):
