Hi Keith
It went really well: This was the basic setup: A rough (30%) scale model of Stonehenge. I just used bamboo for the perimeter ring because I was worried about damaging the field. I've used a small mirror set and a reflector which splays the light out more, so isn't quite as bright as the old one:

I didn't go for the 'summer set' in the end, so the reflector is a bit low relative to the trilithons. Here's the setup working: The mirrors were a little out of focus at the time, but it shows the arrangement:

Most interesting thing is that I'm finding out stuff I didn't know. Take a look at all the lozenge shaped reflections onto the inner face of the trilithons: Because the inner surfaces of the Trilithons have been worked to be flat, you can use the reflections to see if the mirrors are focused rather than having to eye-in all the mirrors from the hinge.

It's a much easier way than I had been using. But it needs flat worked surfaces so I doubt there's a commercial application to today's comparable systems.