I have a buddy from the Air Force, that's working on an HID retrofit project for his motorcycle but has run into problems. He posted this over in a motorcycle forum but has been unable to get any help. Just wondering if anyone here with experience doing HID retrofits can help him out. :-)

His original post:
OK, so I'm finally started on my projector retrofit. I picked up a 3" Bosch projector from flea-bay and a used headlight housing from the same source. I get the projector in and start tearing it down to get rid of all the extra bits (like the auto-levelling gear, etc.) and then start looking at bulb/ballast kits. That's when I realize that D1S bulbs (which this projector is set up for) are EXPENSIVE! So I scratch my head a bit and realize that the box that holds the bulb base comes off, leaving a round base on the reflector with slots for a retaining ring.

Question is: can I install a D2S bulb using a retaining ring like this:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=200458794258&viewitem=&_trkparms=algo%3DLVI%26its%3DI%26otn%3D2&category=36476

Pic of round base attached.