Hey!

Interesting site.

I've never seen it before.
But I did built my in early 2002 I think. I modeled it after the Slamander. My is dual docks or dual bays... whatever you call it.

I used 3/4" MDF from Home Depot and 3/4" threaded steel rods. I didn't use any rubber rings, because I think it is more rigid. Than I paint them black.
Anyway, as for the 3 legs thing. It is not a bad idea. Since I believe that when it come to audio and vibration, odd numbers seem like a logical sense to me.

If everything is equal... even numbers... than the resonance will be magnify.
With that in mind... even though my shelf use 6 legs. I did offset the middle back leg to one side just a few inches. So this way they won't be all equal distance. Think of it now I think I should have offset 1 or 2 more legs on the side a bit.
As for leveling my 6 legs shelf? Well it take a while but I put a nut on each leg at the bottom so I could make leveling easier. And for the shelfs themsleve I use bulleye level in the middle and adjust each legs accordingly.
Anyway, nice DIY link. This is easy to do for anyone and can save a lot of $$$.
Take care,
Buddy

PS
I built 2 more shelfs based on the same design for LPs and storage in my room. They could be taken apart when moving.