Ah, finally the 16000 ray render. This was with the PreviewFinalGather quality, with min- maxrad at 1 and 10 respectfully.

Now I like this pic, it doesnt have good sampling, but it tells me something about the settings I have worked with.

I have still the pleasure to render out a fantastic rendering with the production mode default values, with finalgather rays at 4000+, but it is no rush for me.

RESULT:
Well, the small but important shadows reappeared in this rendering, when the min-maxrad was set to other than "0".

I have been thinking, that I should also try to figure out what min- max rad is necessary for making the smaller shadows appear.