at least you will be putting it to use heating water.
interesting idea, should be a good source of clean energy
that other guy just used it as a toy to melt and burn stuff like an idiot, and wasted a good dish in the process.
rather than go through the trouble of lining a dish with lots of mirrors, if i was you, i would search out an old fiberglass c-band dish and smooth the face of it out as much as possible with a DA and really fine grit sandpaper, then primer it with some good primer and paint it with several coats of chrome paint and then buff it really well till you can see your face in it.
should be able to get a much better focal point and it should be a lot easier to do than line hundreds of small mirrors up, and you wouldn't have any gaps between reflective surfaces so it should give you better efficiency
hope this helps,
Denny