The rayon chenille is threaded plain weave. I used 4 shafts to spread it out some, but it could be done with 2. I then placed the supplemental warp yarn (3 strands) alternately on shafts 5 and 6, evenly spaced throughout the warp (1.5" from the selvedges and spaced 1.5" throughout). I tied 2 treadles for plain weave, one for shaft 5, and one for shaft 6. I treadled with both feet so I could switch the supplemental warp. I tried 6 picks for each supplemental shaft and 8 picks. I still have to finish the second scarf (used 8 picks for that one) so I'll have to see how that compares.
The supplemental yarn is Lion Brand Trellis, a ladder yarn. I couldn't figure out how to include this yarn in the project since Lion Brand is not in the Manufacturers database.