Redraw board outline to reflect 100mm x 100mm goal for main board size.
...and some other stuff I lost track of, or KiCAD just changed/reordered arbitrarily. :-(
Pushed USB PIPE traces on inner-top layer to the bottom layer -- effectively eliminated via stubs (but added via inductance), added a bit of length to those traces, and put them on a faster, outside layer.
Updated netlist, imported into PCB, merged trace segments.