I just read this and it would make sense to me that if you had high glide numbers in mind when writing this, maybe you would make a point that the glide ratio mostly by itself determines the length of the soft shaft…
I will not say that you had not considered this, but reading the text I have the feeling you are moving in a different direction in the book relative to my starting point here.
Also then you would maybe not have the need to insist my idea is infeasible when in fact it makes perfect sense…
I will make a simple argument: double the glide number, and the flying speed doubles for everything else the same. This also means the pull on the tether quadruples. Take a doubling of \omega and quadrupling of T, the moment-to-radius-to-tension ratio \Lambda need is reduced by a factor of eight…. thus the shaft can be a lot longer