Headlight mount for dunstall fairing

Hello.
How does one mount the headlight inside a dunstall fairing?
There are three holes around the headlight opening. Is it supposed to be used with the full shell or just the reflector? If someone have experience to share about these questions I would be grateful!
Thanks!
/D

this is how the headlights are mounted in a John Player Norton, basically they took a shell and cut it about 2" away from the headlight flange. And then fabbed up some angle brackets and springs

That looks very like how these same headlamp units were fitted to some cars, so worth looking at Lucas car headlamp mounts of the same period.