jackstays and tethers will usually keep you attached to the boat, but don't expect them to keep you standing up on the deck
. At 10 knots, you separate from the boat at the rate of 300 metres a minute. A stay and tether means no separation and so an improved chance of staying alive. Increasing the tension on the stays won't do a lot to improve the situation. In the past I used a double tether and hooked onto solid objects. In rough weather
I don't set the jib
or do much to make me go forward. My current rule
is: if I need to use a tether, I should be back in port.