Correct alignment for Fidelity Research 64fx/SPU?

Raul, Thanks for your response.  Triplanar and Reed are two of my favorites, too.  (Naming the only two tonearms on your list that I own and use extensively.)  I have a Technics EPA-250 with two arm wands, one for low compliance types and one for high compliance types.  I have never been able to mount it on any of the turntables I own, owing to the massive base.  I am not crazy about the fact that the arm wand electrical contact to the pivot depends upon those delicate copper prongs. I am sometimes tempted to sell it, but it is too beautiful a piece of industrial art for me to part with it.  Sometimes I just look at it. You, like most others, probably prefer the EPA100.  That would be high on my list.
Bdp, Are you inferring that the Townsend damping trough was your own idea in the first instance?  If so, I am impressed.  Yes, I agree the Townsend turntable is an audio classic.  Its admirers are only less strident than those who worship the Linn, else it would be better recognized for its unique design elements.

Raul, what are your current favorite tonearms? Thanks.

While we're at it, since you brought this 6-year-old thread to the fore.  Jeff1225 said (in 2014) that he had "zero tracking error" using his Mint Protractor with his FR or Ikeda tonearm.  THAT is a feat, indeed, unless he turned his pivoted tonearm into a linear tracker and then had the high skill level and luck necessary to set it up perfectly.  The point being that all of this business with aligning a pivoted tonearm is about compromise or preference. All algorithms admit tracking error; it's only a question of where on the LP surface and how much.

DKarmeli, Perhaps your comparison of SME 3012 to FR and Ikeda was unfair, if you made the latter tonearms wear pants. They sound better naked.

Seriously, no one can argue with your considered opinion based on what you heard in your own system (the best possible data base), but based on reputation, your result is surprising, at least. Maybe that speaks to the abundance of hyper-inflated reputations in the audio world. (You can probably buy three 3012s for the current asking price of an FR66S.) Then too, the SPU is kind of a special case among cartridges. That may play a role in your experience.

Question to those who use SPU:
Isn't there something "funny" about this cartridge, such that the tonearm has to be adapted for proper alignment, or something like that? I think it has to do with the distance between the rear of the cartridge body and the stylus tip.

"50 cm" = ~19.6 inches!!!!
Probably you meant to write "50mm", but I wouldn't know for sure.

I thought I read in one of Art Dudley's commentaries that the SPU required special mounting and/or tonearm adaptation. Dkarmeli's post suggests I was correct; the cartridge directly mates to the headshell mount on the arm wand. So I imagine you cannot either twist the cartridge in its mount to achieve, say, Baerwald geometry, nor move it fore and aft so as to achieve correct pivot to stylus distance. You have to take into account its stylus to mount distance when siting your tonearm pivot.