Headshell Washers : Nylon or Stainless Steel?

Few things are unimportant which are so close to the most critical interface in hifi (stylus >> groove)....

I've been using Nylon washers for nearly 18 months now, mainly for their protectiveness of the headshell finish. The nylon also performs 2 other potentially useful jobs : insulation (breaks possible GND loops - although I've never suffered one before) and constrained layer damping.

There's no denying that setting up a cart accurately is much easier with stainless steel (they don't change shape under compression and end up skewing the cartridge) although, as you know, if stainless steel is used we must be certain that it's 100% non-magnetic.
Another minor source of worry with washer choice are tales of cartridge bolts which have secretly loosened due to inadequate torque. (Although I'm certain the owners would notice this straight away...)

My main question is do the nylon washers have any ill-effects or disadvantages that you can think of?
(e.g could they compromise the rigidity of the "closed loop" - bearing in mind we are using them on top of the headshell not underneath?)
So what is the source of any sonic differences - the damping ability, or something else?

Personally I can't see them having any effect on the closed loop as the cart body is in intimate contact with the headshell and there is plenty of friction there(?)
Please discuss....
John_G....I'd be lying if I didn't admit your response has got me worried. This is a blatant encouragement to the OCD side of my personality... :o)
All the best....

Not to further exacerbate your OCD or anything, but with gear at that level optimizing your settings means tweaking for every session, perhaps for every LP.

....pass the smelling salts... :D :D

Strangely enough, Doug, I lived with an LP12 for 25 yrs and it was amazingly convenient. The Ittok as you know is fixed azimuth so we just had to hope the carts were true. Apart from making summer-winter one-off adjustments to VTF I didn't do anything to the arm at all. Bolts were so tight that you needed to brace your foot against the wall to loosen them with the Allen Wrenches ( :D ) - including the arm pillar grub screw - but then I never adjusted VTA at all so it was never discovered until one day I decided to change a cartridge myself...
Life with the LP12 was magical.... Music just poured out of the system - perhaps slightly flawed in places but the magic was there.
..and all so simple. Switch on, play the music, switch off.
Changing the cart led to changing the turntable and so it began...
My friends have observed that for a number of years i've been as obsessive about equipment tweaking now as I am about the music, so I make a conscious effort not to obsess.
As you can see from the OP the Treatment is working fine... :D :D