What would you do? - Vogue 1099

I still have one more Christmas project to sew up, but while I await supplies, I'm taking a little selfish sewing break and working on my SISC jacket, Vogue 1099.

This morning I got the lining/facing unit mostly constructed.  I always do the lining first so that I can work out weirdness and finalize fit on the part that doesn't show.  This time the weirdness was with the sleeve.

Here is the lining sleeve, constructed per the Vogue instructions.

Here is what Vogue wants me to do - sew the gathering stitches, gather to match, and then tie off the stitches. No stay or any other way of stabilizing the gathers.

And it should end up looking like this, which allowing for the difference between lining and shell, I think it mostly does.  My concern is that it isn't very stable.  Those stitches can slide all over the place, and what a mess if a thread breaks!  Also, I'm not so confident in my square knot tying ability, and ripping open the lining when the knot unties or the stitches pop doesn't appeal to me.  So, I've been contemplating my options.  My first thought was to stitch on a twill tape stay once I have the gathers where I want them.  That would stabilize them nicely and I think, preserve the appearance of just rows of stitching.  I also contemplated gathering with shirring or clear elastic.  What do you think?