Testing a new workflow; I actually used my phone to snap a pic of the cavity, edited the photo removing all but the lip, imported lip image to SketchUp, ran a tight ruby script that converts images to vector shapes, built a deck, scaled it using my micrometer measurements, imported to 123D for additional touchups, exported to an stl, sliced it in ReplicatorG and then printed on my printer.
This solution has been designed to print on most 3D printer build platforms!
You can grab my 3D model here: http://www.123dapp.com/123D-3D-Model/VW-HID-CAP/623071 and use the free 123D app by Autodesk here: http://www.123dapp.com/123d to mod if you like and then export to your preferred format for 3D printing; here is a sample workflow I have used at home designing and printing with great results: https://www.instructables.com/id/Basic-workflow-for-3D-design-in-Sketchup-and-3D-pr/
- Print the A and B cap halvs for both drivers side and passenger side
- Print the drivers and passenger side bracket kits
- Insert the 2 tabs per cap
- Use Acetone on the lips and seam to make them water tight!
- Slap cap on and place the mounts at each end (see images)
- Run a zip tie through the mounts/hinges
- Farfegnugen time!