I know it has been asked before on the list,
Yes it is possible to make the VW logo on the back of your vanagon a 3rd
brake light.

Here is a photo of my conversion:
http://rubatoguy.home.mindspring.com/chmsl.html

The secret? Use a porsche 924 rear side marker light - it just about
fits perfectly behind the logo.
The bulb supplied with the side marker is too dim, so I switched to an
LED 1157 replacement bulb.
(LED because I tried a halogen bulb which started melting the plastic
housing in about 30 seconds.)
Of course, you still have to cut through the rear hatch which is not for
the faint of heart.

Todd
'88 Westy