Your flies are wonderful as usual.
Hans, you are are right that the untwisted floss is fragile, and can disintegrate.
That is one reason I used the silver rib on my Tups swap pattern, even thought the wire is nearly invisible. I wanted to use the floss flat rather than twisted, but knew it was likely to come apart without something to hold it together.
This is a big problem for me, since the 6-inch trout that I specialize in catching have nasty little teeth that ravage my fly box.
L