I’m by no means an expert on this, but I am weaving a scarf that is mostly alpaca, but has a thread of Harrisville Shetland in the warp, and one in the weft. I used it as the light in a D,D,D,L color and weave sequence. I’m interested in the answer to this as well.
That said, I just wove an all alpaca scarf and at the end of the warp I played a little bit. I did about 3/4 inch of HS in a couple of colors, and then some handspun alpaca after that. I cut off the sample, wet it and squeezed out the water then tossed it in the dryer on delicate for a couple of 10 minute cycles. The HS shrank a bit but not much. The whole sample only lost less than an inch both directions. I’ll take a picture later and post. Right now I only have a pre wash I age. Stay tuned!😉