Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
While the precise tension for upper and lower shrouds is unknown to me, I can say that using a loos guage is a good idea.
I've tried to tension a shroud on one side of the boat and then attempt to duplicate that tension on the opposite side by using hand feel. No matter how much I fuss over the right feel, when I compare the results using my loos guage it always shows I'm off.
So, I recommend using a loos guage to verify both side are evenly balanced with whatever tension you decide on.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.