Symposium Ulta Shelf under floor standing speakers - Any Thoughts ?

Certainly worth trying. I can testify to the benefit of well thought out isolation of the speaker from the floor having recently installed the Townshend Seismic podiums under my Magico Q3s. This is more than twice the price of the similar sized Symposium offering but would have the added benefit of isolating the speaker from external vibration (as well as the speaker from the room). 

i guess my one concern having read the Symposium materials is how you level the speaker after removing the spikes as the shelf is to be used flat on the floor. For my speakers at least having them perfectly level is quite critical. The Townshend offers four point leveling

I didn't find a US dealer for the Townshend podiums but had no problems buying them direct from the UK. They are made to order in the UK anyway and will take about 6-8 weeks to get to you. Cost will be $2000 plus depending on the size you need. More details on this thread
https://forum.audiogon.com/discussions/speaker-isolation-experience-with-townshend-seismic-isolation-podium

To Larryi's question on tilt you can get a small degree of tilt but probably would not want to push it too far