Hm9001 has some hard data and some mock it? Ugh.
I have 16 total Nob springs and 4 of the knock off version that are smaller and have acrylic (I guess) tops/bottoms. I have been playing with spring load and trying them under multiple components. To my ears they added some color I didn't like under my Monoblocks but I think they may have improved the sound a bit under my streamer and Dac. Gonna move them in and out to see if I feel the same way over time.
In the end...its a cheap and fun thing to experiment with.