Vintage DD turntables. Are we living dangerously?

Fleib - both the Final designer and Goldmund have clearly stated their design goals. In the Final design their goal is to dump excess energy from the stylus/record interaction to ground as fast as possible. They eschew any form of soft materials - rubber, plastics etc. Kenwood had similar goals with their L07D.
Goldmund have a similar design goal of dumping energy to ground as expoused in their publications on their mechanical grounding systems. If I recall correctly Goldmund's use of lead in the platter was more about adding flywheel mass than the damping properties.
As far as the Transfi goes, I have listened to it at length on both an SP10 & Garrard 401 ( with $15k of arm& cartridge ) and in both instances it was vastly inferior to either a copper ( TT weights ) or stainless ( L07D ) mat, missing big chunks of information and smearing notes.
Unfortunately with mats most folk use them like cables - as bandaids for system deficiencies rather than try to work out the best solution.

Regarding additional platter weight affecting performance, there was discussion of this in the past and I remember at least Lew and I participated in that.

The manual for my SP-10 Mk2A states its performance has "stable load characteristics up to 1 kg tracking force". It also suggests the quartz phase-locked system and DC servo motor torque can maintain rated speed even if 500 tonearms of 2 g. tracking force could be positioned simultaneously.

That seems clear to me that a new platter or heavier mat up to 1 kg heavier than the original platter/mat should operate normally.

It occurred to me that the Walker Audio Proscenium famously employs a huge lead platter, nothing but lead. No CLD or anything. In keeping with my previous post, I must maintain my nihilistic position whilst making any point, but I could say that to my ears the Walker does not commit the sins that Geoffkait has assigned to lead per se. Does anyone think so? Most think it's one of the best sounding tt's ever made, in fact. (I don't own one.) This does not necessarily prove Geoff is wrong or that lead is a panacea, either.

Dover,
Interesting impressions of spiked mats. I'll keep that in mind, although you repeat yourself. Once should be sufficient?

" their goal is to dump excess energy from the stylus/record interaction to ground as fast as possible."

Exactly how is that accomplished, by using a mat of dissimilar mechanical impedance of a record? That doesn't take vibrations to ground, a high percentage will reflect back to haunt the stylus.

This is from a 1987 interview of Pierre Lurne who worked for Goldmund and was responsible for the design of the Studietto table:
http://www.stereophile.com/interviews/pierre_lurne_audiomecas_turntable_designer/

"From the Minimum turntable in 1979, through the second turntable which I designed for Audioanalyse in 1981 and now to the Audiomeca J1, I used the same concept of mechanics. I'll begin with the platter. I agree with other designers that methacrylate is the best material for a mat, and the shape of the platter is the same as the Minimum, which is to say that it is a little concave: it slopes from the outer rim to the center at an angle of 0.30$d. I decided on this form from a statistical survey of a large collection of records. There are actually two sheets of methacrylate, either side of a solid, 8mm-thick piece of lead, giving a total mass of 8kg.

"This construction is something very special. If you know the velocities of vibration in methacrylic and in lead, you can calculate when the vibration is reflected back to the stylus. First, the vibration induced in the record from the stylus tracking the groove goes through the record into the methacrylate, then to the lead, and so on. Each time the vibration is transmitted from one material to another, there is reflection and transmission, and the time taken for each reflection to return to the stylus can be calculated. You need not have all these delayed signals reach the cartridge at the same time. You then get the same effect as with the acoustics of a room with square dimensions—one big resonance. This is no good, and in addition, when a large reflected vibration reaches the stylus, the tracking is instantaneously different. But if you take care of the spacing in time of these delayed reflections—do you understand the concept of the 'Gold Number?'—then neither the music nor the tracking is affected, not at the beginning of the record or at the end.

"We use lead because it almost behaves as a 'magic material.' It has high mass, it has good damping with low-Q resonances, and it has a very low speed of vibration. If vibrations enter the lead center of the platter, they leave considerably later, much lower in amplitude."

Regards,

Dear Richard, For further clarification and to expound on your post above, the current Artisan Fidelity Sp10Mk2 Technics Sp10Mk2 replacement platter (~5kg.) is comprised of a magnesium alloy based lower segment and pure Copper upper section. The platter's internal cross section features concentric damping provisions to help tame stray resonances. Initially, the platters used a slightly heavier (+.4kg.) aircraft aluminum lower section but was eventually replaced by magnesium alloy possessing superior damping characteristics.

Pryso, Acute observations regarding the robustness of the factory Technics Sp10Mk2 A's DC based motor, indeed it (including supporting bearing architecture) is easily capable of accommodating a heavier platter and/or mat over stock. For reference, the factory Mk2 platter weight = 2.9kg. and a respected replacement platter mat, say for example the well known vintage Micro Seiki CU-180 weighs in around 1.4kg.