After years of picking the moment, it was time to permanently lower the stand.  It would no longer be convertible to an X format & would always have to be at least 4" lower.

The dirt cheap chinesium was easier to cut with paw tools than aluminum.  It was more accurate to measure & drill square rods from both sides than a single pass from 1 side.  Lowered it 5.5".  This provided 2.5" of margin around the bolts & is the right height for a 5'10" lion.  Given a few hours, more holes could be drilled to adjust the height.  

The next step was isolating it from the floor.  The C-812 spring was the best solution, an idea emerged for damping it, & the lion kingdom could always avoid playing music at the resonant tempo.

A simple bolt/washer anchored the springs.  The mane requirement is resisting rotation.  

Stuffing  pipe insulation down the springs actually was a very effective damper at the expense of reducing isolation.  Was surprised how effective it was, despite being easily crushable.  The damping could be adjusted with different foam densities.

Slipping off the springs is a real problem.  Gorilla tape is decent, but rubber would be better.  The Xeroshoes might recover some of their $40.

As far as the lion kingdom can tell, it works as well as the bubble wrap used to.  The dog downstairs didn't seem to notice, in testing. The only sound was someone opening a door outside. High notes actually transfer more energy to the floor, because there's less mass in the keys.  A more massive instrument is another way of reducing noise.