The Link showing the Speaker Build shows a method selected as a Sub Support to suspend the Speaker, using a Vibration Control Footer and a Bridging Bar to connect the VC Footers.
A little bot of extra though can really tidy these up aesthetically if one needs to have bling with their equipment.
https://pinkfishmedia.net/forum/threads/my-troels-gravesen-the-loudspeaker-3-build.303400/
The Link is showing the designs available from the Producer of the VC Footers seen in use.
https://www.christiegrey.com/industrial/enclosed-spring-mountings/
My suggestion is that if such a methodology is selected, the following can be considered:
1, Look to see if the devices can be attached directly to the Speaker Base, an adapter thread used in place of the bolt on the top of VC Part, can be looked into to see if a Thread Size can be put in place to match a threaded insert found in the base of a Speaker.
2, A Sub Plinth could have 3 x VC Footers attached.
3, If Bridging Bars are wanted to be selected, using metal only is suggested to be avoided. A Composite of materials can be used, that includes a metal.
4, A material such as a Resin Impregnated Densified Wood Board can also be used for the Sub Plinth suggested in '2' or as the Bridging Bar.