As I suspected, the knobby rayon yarn did not hold up as warp, at leas not at this sett and with flat steel heddles. So, I trashed it and replaced it with a heathery pink Bartlett sportweight. A bit too thick and a bit too pink, but it'll do.
I may rip out this beginning and add more picks to the dark purple stripes; I'm going to sleep on that decision.
In other news, sleeve #1 of Stopover is underway.