First of all thanks very much for your kind words!!!
To answer your questions:
- the circle was cut with a circle cutting compass so the only things I had to do were to measure the diameter and have a bit of patience cutting the disc from a 1mm thick plasticard sheet
- the mg is quite easy too. I't's made out of two tubes (one copper and one brass) of different diameters and then soldered. On the smaller one I've turned some copper wire of appropriate diameter and to avoid to show the spiral too much I pressed it very well with the help of another piece of tubing and a little hammer
- the only problem was to replicate the 16 identical things to fix the hatches. For those I had to create a special metal cutting tool...
Ciao