How critical is the exact placement of the tonearm

Speaking of adjustable, SME tonearms allow adjustments of pivot to spindle distance. I have such an arm (a Pluto -- not an SME).
The funny part is, unless someone gives you the exact pivot to spindle distance, you're stumped if you move the base of the arm...
To make things even more exciting, my arm's instructions, for example, spec 219mm pivot to spindle & 23degrees offset angle... Well, it's either one or the other -- but not both (per Baerwald).
What shoudl I choose???

Thom,

Different offset angles move your null points, but given that we're talking about perhaps +/- a degree (due to manufacturing tolerances), this may not be such a big deal.

Well, the wrong offset angle should increase your degrees of tracking error... so, as you've noted many times, we STILL ain't really hearing the cartridge (or the arm+cartridge combo for that matter).
Really if we could only get these things correct to begin with, analogue life would be so much simpler:)!