I recently made some extra long furled 'leaders' (16') for use as a tenkara line.
I used Spiderwire Stealth Braid 8 lb. A similar braided spectra by another manufacture.

I made a 2 ply tapered leader with 3-5-7 loops in each strand.

I have only fished them a few times but I am happy with the results.
They still have some stretch but much less than a similar line made of UNI thread.
I treated them with a water repellent Scotch Guard spray after fabrication.
I fish them dry, no floatant needed. They don't seem to pick up as much water.

I previously tried to make some out of 4lb test. Very hard to work with, easy to tangle.
The 8lb worked well for my application, for a trout leader I might try 6lb