Hi Bonsai, thanks for chiming in.
As far as those measurements go, indeed the electrical steel core shows good results.
I had a telephone talk with member 'Magic Bus' who has the electrical steel core AVCs for listening tests.
He described to me what he considers as a strange behaviour of them: When the music makes changes in dynamics, these AVCs seem like holding a memory and being unable to let music die out naturaly (lack of music tails).
I 've heard them only while doing casual listening, where I find they are doing very well.
I haven't auditioned them in detail and when I do, I may be unable to notice nuances.
But in the near future I will try to technically investigate further what Kostas has noticed with this core.
Yesterday I received the 0.1mm magnet wire and the priority is to wind the smaller E-I 25 bobbins for the Ni core with some 3k turns.
Measurements will follow soon
George