Thanks for the advice! I know very well that it is best to take the pictures from a low point when taking photos of birds, but I often forget it when taking photos of insects.
I've read the threads before, but I must forgot about the tubes. The bellows is a bit harder to forget. It is inspiring to read about your projects. I would like to attempt to make something like that myself, but I don't have the parts required. I wouldn't like to disassemble a working SD14 camera. But if I find some parts later I might try it.
I have some old m42 macro-tubes which I might try, but then I can't use my sigma lenses.