Upgrade from TW Acustic Raven AC-3 to what?

That is the problem and the core misunderstanding between applied physics and taste. A mix-up or inherent error often happening in Audio. Many discussions in audio thought to be about technical or physical issues are in fact about taste, believe and fellowship.
We have seen some posts here lately which did not content one single technical aspect.
But even regarding taste - you know Oscar Wilde's unforgettable phrase.
But I am confident that Dover as well as me would be able to locate the right spot for a gourmet dinner. And we would choose the chef who really knows what he's doing and would not follow the latest hype or up-written advise which has just opened and presents a Cheeseburger with some golden sprinkles as haute cuisine.

Siltskin, I couldn't even recommend you following my advise. Neither in selecting the main course nor in high-end audio. Extremely expensive, not on the manual at all but special ordered, very special spices and only for the very educated and seasoned taste.
To make things even worse - I stopped eating meat in the very early 80ies........

Dover - as for the inevitable knot in threads (unless to melt certain special material together). I observed that if the knot is made in a special way, it moves onto the outside of the circle and won't interfere with pulley nor platter anymore. I will make a drawing of the knot and send to you by PN next week - when I have my Wacom board.
By the way - you may too give sewing linen a try. It has some very little stretch left (but only noticeable if the tension is too high anyway...), but features extremely high inner damping and a nice combination of grip and natural slippage (sounds like a contradiction in terms, but it really is that way). It works very good on the RX-5000 and even much higher platter mass.
However - surgical silk (I have way too many PhDs among my friends not giving this a try) is a very good choice too.

Knotless thead drive not difficult if you know what you are doing. Sorry about the pun.

I used Japanese embroidery silk which worked quite well by thread drive standards but is so far behind the state of the art that I dropped it as a commercial proposition. The fun part was that a huge range of colours is available - I used red, green and yellow and called it natty thread (with apologies to the late Bob Marley).

Dear Mosin,
Actually i have not sold my TW/Grandezza. Trying to tweak it in the mean time.
Simultaneoulsy, I have learnt a lot from the postings which i appreciate very much.
Rgds
alec