[Saphire]

Lello the bowl is 15.5cm, the inside I lined with the aluminum tape as it stays put being sticky backed.
The diffuser was a bit more difficult to find. I had a clear piece of plastic, which I cut slightly bigger than the bowl so I could score and bend it over the edges, I then cut the center circle out, I also found one of those opaque plastic sleeves you keep documents in. I split the sleeve and sprayed a clear adhesive to the clear plastic on both sides and stuck the sleeve on to it. Then I just cut around the shapes. On the outside I used black duck tape to hold the edges down of the diffuser and also covered the complete outside.
The center hole had to be much bigger to allow the lens to come further forward or come through it to stop flare. When its all put together you can't get your hand inside to put a lens hood on so it has to able to slide down the lens barrel and poke out if possible.
I will be having another play tomorrow to see whether it will work with my ext tubes and my macro rails. It will be great if it does work.