It's been quite awhile since I have knit 6 ply (sport weight) socks. In fact, I can't even remember doing so, that's how long it's been. Or perhaps they just weren't memorable. THESE. These are memorable. Zitron's Trekking XXL 6 ply in color 1846.
For the rib, I believe I cast on 52 sts with a US 3 and did a 2x2 rib. For the heel and foot I found I didn't get the nice, dense fabric I wanted unless I went down to a US 1.5. Perhaps I was extra relaxed on vacation last week and that affected my stitches? Regardless, I want these socks to hold up, so 1.5 it is.