(B) The resultant poles and zeros seem canceling each other but the filter still has a structure. Is something wrong ?
Pole 1 frequency = 0.0497181 Hz
Pole 2 frequency = 2.01809 Hz
Zero 1 frequency = 0.0497181 Hz
Zero 2 frequency = 2.01809 Hz
Ah yes, well noticed. I think I have tracked this down to just a bug in printing of fitting results: It was just printing the pole results for the zeros too. The results for the same fit now read:
Zero 1 frequency = 0.0972455 Hz
Zero 2 frequency = 6.50126 Hz
Overall gain = 71970.1
EDIT: sorry, I forgot that when you write a reply, the author is still by default the person you are replying to unless you change it!