Stillpoints Ultra SS feet fit VPI Classic 3?

The Ultra SS feet are shorter than the feet of the VPI Classic 3. How do you boost height to get enough clearance? Is there a difference in sound between VPI feet and Stillpoints Ultra SS? Thanks!
I tried the Ultra SS under my VPI Classic 1 when I had it. They are tall enough to work. The only thing that hangs down under the Classic 1 is the bearing nut in the middle. Not sure if you need more clearance on the Classic 3. I did not try to thread them on. I just set them under the plinth.

I found them better than the stock feet in my system. The sound was a little cleaner and the bass was tighter/better defined. It was not a huge difference though.

See if your dealer with let you test them out before you buy.
To make it even more difficult, I have Bearpaws under my VPI and love them...they are very large and heavy brass cones. A major improvement