staysail using luff low torsion rope versus wire stay

[Brion Toss]

Hello,
A sail set on its own luff is not a novelty, any more than luff sag with such sails is. The benefit of stays is that they provide the function of keeping the luff relatively flat, without excessive tension, elasticity, or compression. This leaves the halyard to handle the job -- shared with clew and tack -- of projecting the sail in an efficient shape.
Where loads are lower, and sail fullness is desirable (i.e. off the wind) setting a sail on its own luff can be a good thing, but even then too much load and/or elasticity can be a problem. High modulus fibers don't change any of this; they just give us stronger, lighter tools to work with.
Even if you use a high-modulus rope luff, tied to a high-modulus rope halyard, you are still placing a greatly increased demand on the halyard and its gear (note that the furler swivels, winch, and clutch are not designed for this kind of load, and that the load is roughly doubled on the halyard block),because you are asking the sail and halyard to take on the function of the stay.
So at least for a storm stays'l, keep the stay. Then make it as easy and safe to set and strike as possible. A downhaul, properly rigged and led aft, can allow you to do both jobs from the cockpit; the sail is kept on deck, furled, with the downhaul slip-hitched along its length, until you need to hoist. This is simple, cheap, and utterly reliable.
Fair leads,
Brion Toss