tweak the fit of the parts

cases/gps/README.md

@@ -6,14 +6,14 @@ Generated by the Feather Case Wizard.
 - FeatherWings: 1
 - Battery compartment: yes
 - 1/4-20 insert: yes
-- Approximate exterior: 93.9 × 57.3 × 41.8 mm
+- Approximate exterior: 88.6 × 59.1 × 40.4 mm
 - Formats: 3mf
-- Parts: `body`, `lid`, `insert_coupon`, `switch_coupon`, `fit_coupon`
+- Parts: `body`, `lid`, `lid_base`, `lid_accent`, `insert_coupon`, `switch_coupon`, `fit_coupon`
 - Custom cutouts: 0
 
 Run `ruby build.rb` in this directory to regenerate exports and previews.
-OpenSCAD and Blender must be installed. Set `OPENSCAD` or `BLENDER` to
-override their executable paths.
+OpenSCAD, Blender, and Python 3 must be installed. Set `OPENSCAD`,
+`BLENDER`, or `PYTHON` to override their executable paths.
 
 To open the saved Customizer values manually:
 
@@ -23,3 +23,9 @@ openscad -p parameters.json -P gps source/feather_case.scad
 
 The 3MF files contain portable geometry only. Choose printer, filament,
 plate, and slicing settings in Bambu Studio.
+
+For a two-color lid, open `exports/3mf/lid_multicolor.3mf` as one
+multipart object. Assign “Lid base — Filament 1” and “Accent inlays —
+Filament 2” to the desired filaments. `lid.3mf` is the complete
+single-color fallback; `lid_base.3mf` and `lid_accent.3mf` are also
+provided separately.