4 Black Raviolis do work best and that took some re-thinking. They need to be in contact with parts of the chassis.

I can't get my head round Black Ravioli stuff and the silly prices they charge. Shrink-wrapped and sealed foam is what they appear to be. Why not try some fairly dense foam (what goes into large seat cushions - quite cheap from Dunhelm Mill), trim neatly into little cubes or rectangles and off you go...

Yes, the BRs don't make sense but whatever they do is quite different from anything else I've tried (and I've tried a lot of support accessories). No sorbothane or foam comes close. The RDCs don't come close. They do both isolation and damping at once. I wish there was a cheaper equivalent but I've not found one yet.

Yes magnetic feet work well on the Salvation but think you may need to be careful with most equipment Adding magnetic fields is generally not ideal

I agree that some things just don't make sense. One of my tales coming on -

I own a Micro-Seiki CD-M2. A player based on the Philips generic chassis platform that spawned the Marantz CD94, Philips 960 and others I think. Solid rosewood, thick milled top and extra mass in the bottom makes for a VERY heavy machine and that's before the electrical tweaks inside.. Our friendly and very highly skilled engineer also had one and chose to sit it on a aerolam style 'Sicomin' support, a honeycomb interior, clear top and bottom with edging and three viciously sharp spikes. I asked him to fit a Trichord 'Clock 2' which he did. This machine was the first one I'd heard where the soundstage was powerful and three-D, totally lacking the 'bleached' quality in so many early machines. Prior and Subsequent listening comparisons showed that either mod made a small improvement in spatial clarity (horrible words , apologies) and I ended up with both. The weight of the thing I thought would have negated any possible sonic change by adding an 'isolation' platform and the amount of internal regulation, smoothing (and extra regulation added on one of the rails around the DAC chip) should have minimised the need for a clock change (which made little difference to the almost identical CD-94 - the Micro has a separate transformer coupled output stage grafted on top of the stock one and it's this where the magic really happens for whatever reason (transformers self-absorbing ultrasonic and rf muck coming out?).

Anyway, whatever works for the individual.

Micro Seiki below..

As Mike says James, position them according to the weight distribution. I have a valve DAC with heavy capacitors that put most of the weight to one side, so I have two to that side and only one (brass) centred to the lighter side, rather than symmetrical front to back. 

I'll send you a fourth so you feel safe 

Yes they are a bit strange to balance but agree with how they help amazing value for money

I had magnetic support feet for a while (as previously reported, I think).
Under my NAD S300 amp they worked well sonically .... but I am convinced skewed the L/R balance of the sound.  A subtle effect but irritating.
At the time, iirc, Martin conjectured the very strong magnetic field (enough to support a 27Kg amp) might be affecting the circuitry.
I got rid.

I have the Rockin Rollers, but as per inevitability with me   after a while I just cannot be bothered and I don't use them now.  Fancy footers seems to bring out a strange combination of annoying OCD and an anti-foo side of me.  I feel happier and more at ease without them.  Strange but true. 

Well, no.
I change cables / connections as well as moving things around.
But that's just rationalising, I suspect ...

... I used to be a proper footer fetishist.  But there's something about the whole footer / support thing that just kind of annoys me now and has done for decades. ... my dislike for them doesn't have to make sense, OK?!