Dolphin striker tension.

I have been sailing today on my Tiger Shark and found that the dolphin striker has no real tension on it. I understand I should wind on some tension but how much?
Also, the plat form has square section For and aft beams and seams to be quite sloppy, not stiff. Can the striker have any affect on platform stiffness?
Thanks

Tension the striker until the beam just starts to bend [eyeing along or through the beam will show any bend].
This will certainly help stiffen the boat, but there may well be other issues

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