Prindle 18' Shock Cord Replacement on Trapeze

Hi! I'm relatively new to sailing catamarans and I'm replacing the shock cord & lines on my trapeze. I was just wondering how tight should the shock cord be? (I wasn't able to get a sense based on what was on there already because it was pretty stretched out)
Tight enough is when there isn't a slack in the lines that lets the hooks slap you. A fresh shock cord is something your should replace fairly often. After taking up the slack a couple times, it's time for replacement. Tighter is better, and shock cord just loses it's ability to retract after a year or two.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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