Update 9 Oct 2012:
It has been a while but I did manage to get the projectors fitted and mounted properly into the headlight bucket.
I ended up using 1/8" thick aluminum stock and 1 1/2" standoffs to mount the projectors directly to the original reflector mounts. The holes in the reflector mounting brackets have holes in them that 8-32 screws fit into perfectly so by using 2" long bolts, stand offs and nuts, I was able to fabricate two pair of aluminum plates to mount to the projector housings using the same screws that attach the two halves of the projector together. Most everything is available at Home- Lowes with the exception of the long standoffs- those came from McMaster Carr because Home Depot did not have any stand offs longer than one inch.
Once assembled, the entire projector mounts in the headlight housing using the original plastic nuts that both retain and align the original reflectors. That means that the same adjustments can be used on the new projectors to aim and align them in the original housings- to the rider it would appear stock.
The projectors with the adapter plates, standoffs and original reflector mounting tabs:
The projector assemblies then mount into the housing exactly the same way the original reflectors did:
The location of the projectors is important so that the HID socket is near the center of the original headlight hole so that the rubber boot can seal everything. That is also why the standoffs had to be so long- to push the projectors forward to allow the back of the projector, and therefore the back of the HID bulb, to be close to flush with the back of the headlight housing.
Note that the projectors will move around as they are lifted and moved left / right with the adjusting screws so I do not know exactly where the backs will align regarding the housing until they are installed and properly aimed. At this time, it is just a rough fit with the rear rubber seal taking on any movement to allow the alignment later (on the bike).
This is what the projector looks like in the housing without the internal shielding housing installed. I was originally going to use them this way but even blacked out I think it is probably too crude to leave like this:
With the inner housing shielding back in place I think it will look better once everything is painted flat black:
I can also buy projector covers to cover the front of the projector housing and have it blend in with the plastic housing cover better. Again, everything will be flat black but at least the shields will prevent the mounting brackets to be seen.
Next step is LEDs inside the housing.
Brian