@ozzy I have done extensive research into mounting Speakers on Sub Plinths from a Single Tier Design to a Triple Tier Design.
A Single Tier Design with Spikes only as the Support for the Sub Plinth, is going to change how the End Sound Produced is perceived to the Speaker being in contect with the Floor only.
The Single Tier Design with Spikes only as the Support for the Sub Plinth, is in my experiences had, not able to Tidy Up the End Sound produced to the same level that other Assemblies of a Sub Plinth is able to create.
My experiences to date, allows me to strongly suggest a Suspension Type Sub Support is the method that really starts to deliver the Tidy Up of End Sound that is wanted to be maintained.
How one builds on with a Sub Plinth, incorporating the the suspension footer/ additional suspension footers is their choice.
I get exceptional results with a 3 Tier Assembly of a Sub Plinth with 2 Tiers separated by suspension footers.
All designs can be DIY and not cost stupid amounts of Monies.
My most recent experiences are enabling me to strongly suggest Wood Materials as a Sub Plinth are very very good.
The Wood Materials to be suggested are a Resin Impregnated Densified Wood Board, this material type can be found supplied from a selection of producers, but is not mainstream common as a material.
The Link is the cheapest way I know to introduce a person to have a Pneumatic Suspended experience of a Speaker, and obviously owning a few of these if not permanently used is not too bad a ancillary to have in the tool store.
https://www.amazon.com/s?k=inflatable+levelers&crid=3VVXW08BZ0EXZ&sprefix=Inflatable+levelers%2Caps%2C252&ref=nb_sb_ss_p13n-expert-pd-ops-ranker_2_19
3D Printer Anti Vibration Feet are becoming quite common and are looking to be quite affordable and much more fitting as a Suspension Footer to be used with Audio Equipment, for some Speakers the weight capacity might be limiting. Some designs I have studied do look like additional parts can be added that should upgrade the weight load that can be taken.
One 3D Printer Footer seen has an design that is equivalent for the suspension from another Company directing their sale items at the Audio Market, the weight capacity for the 3D Printer model footer is not known, but approx' $340 separated the purchase price between each.