I made these for my RSX project, but I figured I would go ahead and share the love now.
I'm still not sure if I will use them or not.
What you need:
Zip Zaps Box
Masking Tape
X-acto Knife
Pen or Pencil
Dremel
Sanding File
First, you cut a chunk of the box out. I used the corner, because the tail light lenses on the RSX wrap around. The Skyline for example would be easier, because all you would do is cut out a circle and your done.