Correct alignment for Fidelity Research 64fx/SPU?

In my experience a 3012-r + SPU beats the pants off any SPU + FR combination, including the 66s & the recent Ikeda arms. The FR mount doesn't have the flexibility of the SME and as you noticed, short of a new arm board you won't get the proper tracking angle for this combination.

Lewm, I've been at this for years now and spent enough time comparing arms and cartridges on high end tables to finally settle on the 3012-R, and yes the cost is also important. At any given time I have 16-20 arms setup on various tables, aside from sounding great the 3012-R is the most flexible and most economical too.

Syntax, it's not a fact at all, only your opinion. Technically the 3012-R's
sliding base makes them much more flexible and accurate setting tracking
angle on various cartridges, you're much more limited in your cartridge with
the FRs. Where do you get limited to Shure system from? I have everything
from Shure to Neumann DST set up on a pin modified 3012-R and they all
work and sound fine.

Yes alignment is an issue with FR arms with many cartridges, fx and steel
tubed, that's a design flaw. You can also add arm leads, mats and even belt
tension to your list of things that can affect comparisons. Garrard's
vibrations can be mitigated with a properly designed and built base
and even go further by having standalone arm bases which allow more
flexibility of alignment for FR/Ikeda arms. But the Garrard is colored
and not the ultimate in resolution making this kind of assessment difficult. In
my case I lived with FR66s and 64s for many years and had them sitting
side by side with 3012-Rs on the same tables, SX-8000mk2 and American
Sound AS-1000x, the most neutral and natural sounding table I heard or
owned. I find the 3012-R superior, specially in the low in the lower
frequencies. Let me add that I don't like the sound of silver wires and my
FRs are all wired with it.

Lewm, the SPU comes in its own fixed headshell so don't have ability to change the tracking via the headshell like a standard cartridge. In case of the SME the base is also adjustable but not with the FR. In this case you need to move the arm hole on the board for optimum tracking angle.

Lewm, That's correct, it fits directly into the bayonet mount of the arm. The only twisting you can do is for azimuth adjustment.