Turntable isolation

Springs or sorbothane can both be brilliant at isolating the turntable from resonances but only within a fairly narrow movement/frequency band. Project and Roksan have both successfully used sorbothane/rubber decoupling for years but neither would work well if the they were used in a car, on a ship, or a plane. You really need to first look at what your turntable is sitting on. In turntable terms it’s probably wobbling like crazy.

As chayro said it’s unlikely any deck can withstand springy floors so a carefully located wall shelf (walls resonate too) may well be the best option. Alternatively, you could try to isolate the table that the deck itself is sitting on.

The good news is that whatever method you chose - tracking performance and hence sound quality - will improve.

I know some people with HW-19's took out the springs and used sorbothane/rubber in its place

I made a video some times ago.https://www.youtube.com/watch?v=mcoBxztdA1sFrom 0:40sec. you can see some measurements with Sylomer.
Sorbothane is not long-therm stable.

One possible issue with any turntable springs is that they aren’t the correct spring rate to be able to handle the extremely low frequency of the seismic vibration. It’s neceassary to get the total Fr down to say, 2 or 3 Hz, ideally, before very good performance kicks in. Alternatively, you can load the existing springs with a heavy slab of granite to reduce Fr.

You might try what was used to good effect in the final iteration of the TNT turntables, that is, squash balls. At each corner a properly sized piece of wood with a central indent on top (such as you can make with a large counter-sink, a spade bit or a forstner) can hold the ball in place with the TT on top of it. Adding something heavy underneath can complete the base: a sandbox, a thick butcher block, a piece of granite or marble.