Fidelity Research FR64s Headshell dilemma

I use 231.5 P2S with the 64S and Baerwald. I use the Arche Headshell that allows me to slide the headshell in and out giving me about an extra 10mm of adjustment. This essentially makes the headshell longer.  At 231.5 and Baerwald the cartridge is straight in the headshell, and the Arche gives enough adjustments where my Koetsu is still tucked under the headshell instead of awkwardly sticking way out in the front.  I use the Smartractor and tried Stephenson and UNI-DIN and still think this setup sounds the best for me.

advanced&karl_desch, Assuming that you are not familiar with
Arche you can buy extra insert pieces on which the cart is installed.
This way you can use the frame as base and pre-adjust as many
carts as you like. It is like owning many headshells in one.

And I had the opposite problem to the OP - had to push Decca Reference all the way back in AV101 on FR64S at 231.5 P2S and even had to push the the AV101 loosening the azimuth screw and finally remove the gasket (anyway recommended by the FR manual) to get a reasonable alignment. I was using the Nerve Audio copy of the Dennesen protractor and sort of cross-checking with the Mint (Decca’s have no cantilever so only the arc). My P2S is actually a bit shorter, closer to 231mm as this is what my setup allowed. I guess much depends on the cartridge as all have different "effective lengths".

Bu why do you change manufacturer recommended PS from 230mm to 231.5 mm ? 

This 1.5mm can be easily adjusted in the headshell with recommended 230mm PS

Dear chakster, what you overlook is difference between zero (0)
points on the record surface between those two geometries.
Bearwald has the best áverage values for all surface places
while Stevenson has better value for the inner groves. You may
have records hith inner groves which ''ask'' for Stevenson. But 
the most people prefer better solution (values) for all groves. 
As I mentioned before you attribute to manufacturer to much
''authority'' with illusion that they know better,
By scientific arguments used by Kessler and Pisha all 22inspected
tonearms  have sub-optimal solutions for prescribed parameter.
I hope you can find their .article (Audio Jjanuari 1980) and see
for yourself. ''Belief'' is not an scientific argument.