The length of the rows has very little influence on the stress to which anchor points are subjected. In fact, the end result of the forces borne by each pole is equal to 0.
There is no accumulation of stress along the length of the row.
The stress on anchor points is mainly influenced by the above-ground height of the trellising and the gaps between poles.
These same criteria should be taken into account in order to determine the resistance of the poles themselves.