Small update. Today I measured tether drag and tether “belly” (bending due to centrifugal forces on tether). I think this is a reasonably scaled model of a rig that could have been hundreds of meter long shaft.
In this picture you can se the tether drag shown as a “splay” angle between the two tethers at top and bottom.
In this picture, you can see the “belly” shape.
Here is my estimated “belly” size, 5 cm on either side. My graphical solution from the photo gives me 4.5 cm!
Cool stuff.