Testing the Yamamoto HS-4 Carbon Fiber headshell.

Received the Yamamoto HS-4 Carbon Fiber headshell today and tried it on my 12" Jelco 850L. I guess this is a common upgrade path for many Jelco users so I succumbed to temptation.
Turntable is a modified Garrard 401 in a slate plinth on a maple and concrete support with new third party bearing, platter and idler.
I tested it with my Decca "Garrott Brothers Microscanner" Gold with new line contact stylus and Decapod.
Three records were played. Ketty Lester - Love Letters (1962), Cole/Davinport/Tate/Dickenson - French Festival Nice France 1974, Buddy Tate - The Great Buddy Tate (1981).
I played sample tracks from the records before swapping the standard magnesium Jelco headshell out. From the first needle drop using the Yamamoto, there was a soft grey veiling. Not a great start. There was definitely greater depth and improved bass - I could hear the kick drum pedal hitting the skin in a very specific location and acoustic bass was well delineated and easier to follow. Soundstage was more of a wall of sound with greater height. I remember the same effect using grey plate Sylvania Gold 5751s once which are acclaimed but not to my taste. Female vocals didn’t have the articulation and airy projection I normally experienced and it was that which forced me to stop going any further and I duly put the original shell back. The greyness was gone, replaced by a transparent black background and what I can only call a vast increase in precision and focus. I deliberately didn’t mention the mids and highs with the HS-4 simply because they were compromised and wholly unsatisfactory. With the Jelco, the tremendous detail returned: The color and metallic shimmer of cymbals, the beauty of vocal inflection, instruments speed and clarity. Piano hammers sounded fast and believable. But most importantly, dynamic range now soared with startling realism. That bass drum is not as clearly evident and it is the one area I’ll give to the Yamamoto. Make no mistake though, this carbon fiber headshell was an enormous fail for me. I can only assume the material imparted its soft plasticky sonic signature onto the music. Not recommended.