I just tweaked the Gyrodec again, 8mm diameter by 3mm sorbothane glued to 1mm thick rubber place on the top of each suspension pylon and then the supports for the chassis (the threaded adjusters that the springs are normally on) fitted over them. This is to try and get some form of decoupling of the chassis from the legs which are attached to the pylons through the spider. Also my feet sit on small indented discs, I have glued some 2mm rubber under these as well.

Listening tests are that initially things sounded a little dry, then after listening to a few tracks I realised what has happened. There is obviously some form of better de-coupling due to the sorbothane/rubber in the pylons, the result is that there is less microphony (feedback) going on through the chassis enhancing and colouring the music. So bass is more defined (less bloom), overall more clarity and separation.

So a positive result. Not perfect, tapping on the shelf with a record playing still induces a noise through the cartridge, but I would estimate a 50% improvement. The only other thing I can think of is to replace the Gyrodec metal feet with some form of rubber feet, possibly firm sorbothane. I am going to search for some that may be a similar height and could be fitted in some way to the pylons.