The bearings are not carrying any more weight, so why not use beetle ones..
Here's my solution. Full write up at
http://www.fastbug.net/node/219
Using this image you can see the difference between the beetle spindle and Porsche hub.
Spacers where created to go into the hub to hold the beetle bearings. The hub was shortened at the back edge and a spacer inserted to hold the seal.
The result? Custom hubs that use beetle parts, but allow the mounting of a Porsche disc, and with minimal track increase.
Chris aka CSP