No. Calm nerves is never worth it alone. Here is why..
Say you have it at level 40 = +4 calm nerves. To level 40 took you 8 upgrades, or 16 bonus token cashins. The opportunity cost of this piece is thus 16 SP.
The max level a SA has value is 10. I'm assuming you have custom. Thus to get to 10, now you need calm nerves to 5, so 5 + 4 + 1 = 10. This implies the value of the piece is to go from 5 -> 9 (not 6 -> 10, the custom is a given here).
That value is 3+4+4+5 = 16 skill points.
So you "break even." So why not have a full 16 games of +5s?
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The only time a +1 SA +0 stat piece is worth it for ANY POSITION is if it is the last SA in the tree. Remember that rule
