- 30% of the crew (or everyone if you single hand) must have a tether leg of no more than 3'.
- Every tether must be less than 6'6".
First off that means you can, and perhaps should have tethers less than 3'.
This tether is only 30 inches, is attached well in-board, and I'm well outboard. Of course, I had to climb over the high lifeline.
At the mast in lump weather I sometimes go even shorter. How about a vertical jackline. Every boat should have these available in the form of halyards, though mine are fixed (they serve an unrelated tangle-avoidance function).
Additionally, I see no reason they cannot be longer in certain cases. My other leg is 8', bout right for the broad bow of a cat. I can imagine much longer on bigger boats. You just have to use the length intelligently.
What about smaller boats? I was fooling around on this 27' mono, using Amsteel jacklines, and concluded that the longest leg should be 3' and the shorter perhaps less than 2'.
I like custom sizes. These are fabricated from 8mm climbing rope with sewn splices.