I think it’s possible there’s something else here. Is the shim just about VTA, or does it also change the effictive mass of the tonearm? I.e. solve a compliance issue?
I don’t know really. It’s just necessary to have the arm strictly parallel. And I think that mostly Rega wants to discourage buying other brand cartridges.
My dealer sells Rega since 30 years and sells a lot of Rega turntables with Dynavector and Lyra . Of course some prefer the package.
The effective mass is not related to anything not pivoted
Ah, I was thinking of a shim between the cartridge and the headshell. You’re of course talking of a spacer under the armbase.
Absolutely. I wonder if everyone had understood first, if not a lot of discussions with a lot of misunderstandings 
I was talking about the spacer at the arm base since the beginning.
I did understand, hence the warning about the ceramic brace when re-fastening the arm to the plinth
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FR…be flattered…you have a whole forum worried about your ceramic brace!
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Is it? Rega seems to think not, and they’re probably right when you look at the maths.
Consider that the VTA of different cartridges can vary by as much as 10 degrees, and that of the cutting heads by 20. So the fraction of a degree in angle at the stylus that raising the arm 2mm at the base will make will hardly be of any significance.
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These figures seem extraordinarily high, verging on unbelievable (from a non-user of a shim!).
Rega give these or similar numbers in the book. They are particularly unimpressed by cutting head accuracy
In anycase, we do not use shims!
FR…you have the courage of your convictions (hope this translates okay)!..cannot wait to hear about how it works out for you.
This is an interesting read. Sources are referenced, although I didn’t read those.
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I prefer to trust Michael Fremer than Rega, sorry to say. It’s absolutely not my conviction but the experience of a lot of users in the world.
And Michael own position on that, and experience.
He reviewed a lot of Rega turntables and tried many non Rega carts. I asked him and he advised me to use 2mn spacer with the Kleos.
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Here is the recommendation of Jonathan Carr, well known audio specialist. He recommends 3,4 mn spacer for Kleos on Rp10.
My dealer suggested 2 mn. I will see if it’s enough.
“: The Kleos was designed to have a vertical height (headshell underside to stylus tip) of 17.377~17.48mm with VTF applied. Let’s say 17.4mm. I believe that the Rega cartridges are 14mm high, and Rega’s tonearms and shims are designed accordingly.
IOW, you probably need to bring the base of the Rega tonearm up by 3.4mm to make the Kleos level.
If Rega cannot provide a custom shim for you, I would bring one of your shims to a machine shop. Ask them to caliper the inner and outer diameter, then have them make up a custom shim of 3.4mm thickness (if the machinist can make 3.43mm thickness, even better).
If you have a range of tonearm shims made to varying thicknesses, say 0.3mm apart (or even 0.1mm if the pricing allows you to make 10 or a dozen), you have a fairly predictable method of experimenting with SRA. Shims of more than 3.4mm thickness will result in tail-up SRA with the Kleos, and shims with less than 3.4mm thickness should result in tail-down SRA.
Or as Elizabeth said, you could install the two Rega-supplied 2mm shims, then add an LP mat of 0.6mm thickness to take up the difference.”
In the linked article, there were also luminaries arguing for VTA adjustments, but their claims didn’t hold up. I am still really curious why you have a Rega though if they don’t even know the basics of TT building
I wouldn’t actually call it a referenced review…
…but…
The geometric calculations clearly demonstrate that SRA is not critical, just take reasonable care to set a good compromise.
This fits with my experience, when I had a P9:
DV XX-2 II on RB 1000 on P9 sounding better without rather than with shim.
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…maybe the explanation is differing priorities…rigidity v absolute accuracy in setup?
Sorry, not getting what you mean 
Edit: like FR possibly putting more priority on minute angle details rather than Rega’s rigidity philosophy? If so, it would not answer the question, I’m afraid
Agreed…but, it’s the empirical evidence which will answer the question…‘does a mix and match approach work in real life?’…
…FR will let us know!
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This is just a description on how to do it, not a recommendation to do so. And certainly not an explanation of why you should.
Also I find it very strange that he goes on about those fractions of a mm when records have different thicknesses, so it will never be exact anyway. And a warp will likely make a bigger difference than the shim!
I think what @Suedkiez says makes sense. You have a Rega, which has a philosophy that’s different. Maybe it makes sense to follow that? Or consider a brand with a different philosophy? Many tonearms allow you to change it.