Kai,
All very interesting stuff. Dynamic soaring utilises wind shear to power flight so I wonder if what the spider does is more akin to "dynamic kiting" whereby it projects its silk up through the lower levels of slow moving air to the high speed flow. With the L/D @ 0/1 it gets lifted up and along like the downed pilot recovery system as shown here:-
https://en.wikipedia.org/wiki/Fulton_su ... ery_system
This system uses a balloon to get the line up to the level for the aircraft which would be the equivalent of the high speed air flow that the spider uses in its system. So nature got there first with this one.
Tony