Is there any adjustment possible of pivot to spindle distance and have you checked it is actually 212.5mm?
What alignment is being used on the Naim card?
There are a variety of alignments available on various templates. The difference between Stevenson DIN and Loefgren B IEC is greater than the “error” we’re being shown.
There was some disagreement with the original Aro as to whether it should be 212.5 or 211 and I think either could be achieved with the original Linn arm board.
Good questions Yeti
Yes the spindle to pivot is 212.5mm and no the arm can’t be moved positionally on the deck. Those were the first two things that I checked.
As to your other point all I can say is that the sound quality improved and surface noise lowered when set to ARO set up template/ guide.
Simon and I did a seperate check with the Project cartridge alignment guide which sets to Loefgren…
Please excuse my ignorance in these things, I don’t use a turntable but find this fascinating. Could this sort of misalignment cause damage or accelerated wear to the vinyl? I know some pressings are extremely valuable - just curious…
That’s more associated with Azimuth ( the cartridge being horizontal to the LP surface) and anti skate error. Not enough anti skate and the inertia pulls the arm toward the centre overly wearing the inner groove . Too much anti skate and the opposite occurs. Although most modern cantilevers are stiffer than of old so aren’t as sensitive to it.
I also like to set the rake angle to match the way LPs are cut on the lathes to around 92 degrees. A simple digital microscope with protractor software can achieve this.
No, provided it’s not grossly out, it just changes the null points and arc of increasing/decreasing tracing distortion across the LP record. The only way to make it “perfect” is to trace the stylus across the LP radially. Unfortunately radial tracking tonearms come with their own unique set of problems, so there’s no panacea.
Or get a thales simplicity arm
This seems to be a very optimistic assessment. According to Rega and Roy Gandy, there is a lot of variation in the cutting.
The Record: The VTA of a record cutting stylus is set to give the best continuous cut of the lacquer. Records are cut with a VTA which varies between 0° and 20°. On an individual record the VTA will vary by 7° or more, depending on the type of cutting head used, the depth of cut, the musical frequency and the lacquer springback. The VTA of the groove on every individual record varies by at least 7° over the record. Every record is cut under 20°.
Fair enough. I was following Fremer’s recommendations. Seems to work.
Nothing wrong with setting it correctly within the ballpark, we just shouldn’t expect great precision to one degree with anything vinyl
You need to get it spot on with vinyl, in the ball park really doesn’t cut it and even the smallest bit out makes a difference
Anti skate is the area where there are the most differing theories and methods to set 
Did you observed too that this 92 degree angle gives an optimal sound ?
It’s a thing that I was not motivated to do . But maybe one day.
When it comes to cartridge alignment you actually have better and worse answers, unlike with VTA where ballpark really is good enough.
That said, running the Aro 2 outside of Baerwald geometry makes this a direct descendent of the original Aro, which was always out unless you used a Linn or DL-103 MC cartridge - which is true for many of the posts on this forum.
As such, I’d argue Naim not caring about geometry in the Solstice would definitely make it a true Naim product. 
Except that it’s impossible if cutting angle has a wide variation, every record has a different thickness, and geometry does not allow for entirely correct alignment other than two points on the record, whatever alignment you choose.
Of course it should nevertheless be adjusted as good as possible, but obsessing beyond that is pointless
The pictures from @Cohen1263 show the ARO2 out of line on its own Protractor. Something is not right here… 
HQ are looking at it now Ian. Richard will report the findings for sure.
Which is why I bought a P10:
Set the bias adjustment slider to the same figure as the cartridge
tracking force pressure quoted by your cartridge manufacturer. Note:
This is not critical and a figure between 1.0 & 1.5 will normally be
suitable for moving magnet cartridges and 1.5 & 2.0 for most moving
coil cartridge
I don’t doubt that it is critical for some decks, I just love the 10 min setup.
Until you find your cantilever isn’t pointing straight ahead any more, OK that was on an early RB300 but I won’t trust bias scales since then.
Michael Fremer wrote that cutting angle will have been between 91 and 93 degrees depending on manufacturer.
I tried lowering the pivot end of my ARO earlier so that the arm tube was parallel to LP which would make stylus rake angle just below 90 degrees and the sound was more shut in. Set back at 92 and I’m leaving it. Sounds great!