Rose Rib Socks--Getting Started

You probably think that I've abandoned knitting my way through Sock Knitting Master Class. Not true!
But I did get sidetracked for a few weeks. I'm back at it now and have started Evelyn Clarke's Rose Rib Socks, pictured below and on page 80 of the book.
Evelyn used two skeins of  Lorna's Laces Shepherd Sock (80% superwash wool, 20% nylon; 215 yd [197 m]/2 oz) in blackberry.

According to Clara Parkes, these socks have best stitch definition if worked in a well-rounded yarn (Shepherd Sock is 4-ply), but a springy two-ply yarn would give equally attractive results. She mentions that the 20% nylon provides welcome reinforcement to the openwork pattern and bottom of the foot and toe, and that this simple pattern allows for a bit of color variation, although the stitch pattern will look best in a solid or semisolid.
I looked through my stash for something suitable and found a gorgeous skein of Primo (75% extra fine merino, 20% cashmere, 5% nylon; 385 yd/100 g) that Plucky Knitter (www.thepluckyknitter.com) donated to the Sock Summit teacher's bags. This yarn is a round, tight 4-ply with subtle color variation, so even though the nylon content is a bit on the low side, it promises to work beautifully. The rusty color I have is called Sticky Toffee. Yum.

I get the suggested gauge on my size U.S. 1.5 (2.5 mm) Signature needles. To ensure that the upper leg will fit my calf (which doesn't have a well-developed muscle), I cast on with size U.S 2 (2.75 mm) needles and plan to switch to the smaller size when the leg is half done. I'm following the size for the larger socks with a foot circumference of 8 3/4".