Been watching this thread and the one on CN.
The whole problem is moot unless you have something that will cause "resonant" vibrations in the first place, ie wind, mount motor or ground based, and you need to define that first.
Dealing with an "oops i bumped the mount" moment cannot be handled by any sort of mounting ( and is not cost effective )
Also you need to look at the problem as an entire chain, and doing vibration analysis on something like that is soooooooooooo difficult in theory, as to be almost impossible.
In my case, if i have my 10" Meade LX200 on a wedge, a rat cage would be the least of my problems.
The only way to truly "test" if you have problems with your "entire setup" would be to fit a few accelerometers onto the bits and see what they report. Accelerometers are cheap as chips these days.
Also, as to requiring a large mass in the ground, i dont always think thats best, esp if you have ground vibrations.
To me, if you got a long piece of pipe and a hole borer/auger,
you could bore down say 2 metres and drop in the pipe and then backfill.
Its not going anywhere, and also has a much lower footprint for transmitting ground pressure changes ( moisture change or vibrations ) to it.
Have attached a piccy of an early pier i did this way with wood.
The hole i made was limited by my shovel size, but an auger would have been better. It never moved until it started rotting
an old telgraph/electricity pole would be perfect
Andrew