Are we fooling ourselves about jacklines and tethers. The illustrations posted and the general consensus is that jacklines are rigged along the main deck inboard as much as possible. That is usually less than 2ft from edge of boat in most cases. ......
You make a very valid point.
is to have the jacklines as close as possible to the centerline (one per each side), plus a tether that has multiple connection points - thus able to lengthen or shorten the 'effective' length of the teather.
Since my jacklines (tubular webbing) are nylon and therefore somewhat stretchy (dampens impact) and are not 'taught' between their ends ..... my usual is that the jackline is 'raised to me' (very short tether position) rather than using a typical long tether and taught jackline. (I used to do mountain rescue, so the slack jacklines to me are 'de rigueur', 'old hat'.)
I use the Wichard double-action 'safety' hooks on my tether - two 'motions' to open as I dont want the extra time to unscrew the 'gate' of a locking carabiner. http://www.wichard.com/fiche-A|WICHARD|7005-0203010101000000-ME.html (available through Sailnet store).
On the mountain you usually have time to unlock a carabiner, not always so on a boat.