First I created a single-player (PvM) char with hero-editor and then I did several tests to evaluate each of the possibilities to sock this bow and I concluded that sapphire is really the best choice.
Because your cold damage slows non-immune monsters for 3 seconds without need mana, really even recovering it.
Also, cold damage will also work in PvP, which a Pskull would be useless.
The other options can even increase physical, elemental damage or AR, but with a chanter fire and AR is achieved without needing use soj (and does not cause delay).
The poison damage is ridiculous due to the amount of HP of the monsters in Hell , Same for lightning damage.
Even diamond seemed better than these last 3 options, because 68% ed (physical) against undead increases life/mana steal, but doesn't slow enemies again, dont forgeting in PvP the opponents are human.
Explained why sapphire is the most logical choice to use in this bow.
Reference:
https://forums.d2jsp.org/topic.php?t=72586461&f=57&o=0#p489696020This guide is highly instructive, however I did not agree with the choice of fitting suggested by the author (Pskull), but for those who have never built a bowazon in the classic it is a great starter reference