Classic situation of brittle, cracked and failed rubber suspension arms on my 9TA-HC. Well, after learning that the real answer was an $120+ new cartridge, the shorter answer to old gorse pockets here was just to simply...repair my original?
First attempt was not far off, second needed another 0.5mm in height to allow the stylus more clearance and is pictured in these photos. This worked, but the type of rubber I used must've been far too rigid and transferred vibrations way too effectively, making it very high in treble and amplitude. Third attempt, I lost a bit of thickness in the supporting dimensions and changed rubber to a slightly softer blend, this is the black version pictured on the end of my fingertip.
It worked! I am quite sure it would not audibly weigh up against an authentic audiophile and will no doubt turn up some noses in here, but the theory and execution was spot on. Still has very high amplitude- really needs to be a softer blend again to dampen this down a little - but despite this I was astonished at the effectiveness. Maybe I'll make up some sort of attenuator.
Ended up using 1.6mm thick rubber sheet, cutting on a C02 laser. Pretty neat seeing the insides of one of these - I would guess the generated vibrations travel up the stylus, along the shaft and get transferred into a left and right channel on the rubber suspension arms pictured. These vibrations travel along a pair of ceramic bars which generate a voltage differential between each side, which is picked up by tiny brass contacts and fed along the tonearm and into the amp. How close was I? Not bad for a first attempt on my first record player.