Mft 's suggested VTF: Follow or not to follow???

Dear all,
I would like to seek your advice on this issue: Should we or should we not always follow the manufacturer's suggested VTF???

I've been dealing with female vocal's sibilance since like forever and NOTHING seems to help totally eliminate the phenomenon of sibilance pulls to the left channel !!! I have read numorous posts and try them all without achieving the level of satisfaction i expect.

I ran though this problem with an Avid Acutus-Origin Live Conqueror tonearm - Koetsu Urushi, SME 20/2 - SME VI.Vi - Lyra Helikon - Project Perspective - Sumiko Blackbird on discs like Holly Cole " Dont Smoke In Bed", Diana Krall " From this moment on"...(All of them are Classic Records). Using Feikert Protractor AND Wally's universal tractors (have settings for most of popular arms), I can achieve rock solid imaging, huge soundstage and make the speakers totally disappear with LP playing, EXCEPT making that siblance disappear ! With other discs like Classical, Jazz, 60s-70s-80s-90s pop/rock, I DO NOT detect (or extremely rare) distortion/mistracking. ONLY Female vocals, especially discs from Classic Records.

I'm very careful and patient in setting up turntables, also played around with VTF, VTA, Azimuth...etc..etc but i cannot get rid of that annoying sibliance. On some discs, that pull-to-left-channel never seems to happen, but it always happens to some degree in Classic Records' female vocals. Until now, i'm so frustrated I dont know which to assump: my setup or those discs??? Would greatly appreciate if someone can point me to some directions.

(I have the tendency to refuse in believing that Classic Record's mastering-cutting head is cutting these bad sibilance in discs like this..hm..)

now, a question also emerges during my LONG setting-up sessions:
ALL of the cartridges-arms-tables combo that i have tried (listed above)only pass 2nd track and NEVER get passed the 3rd Anti-skating track on Hi Fi+ Test record (the 300hz, 14dB). With all other parameters (VTA, VTF, Alignment, Azimuth..) carefully checked, IF i use more VTF (up to 2.1-2.2gr for Lyra Helikon, 2.3-2.4gr. for Blackbird), the cartridges tracks a bit better.

So..Should i use the VTF which helps the catridges track better or just stick with what the manufacturer suggested VTF and forget about the HiFi+ test record? My concern is that those sibilances are mistrakings, and that will ruin my records ( i care more about records than cartridges !!)

PS. Even with the cartridges tracking better, the sibilance issue doesnt improve much.
Thanks in advance.