Mottled Wave Socks

I finished these socks about a week ago (previously mentioned here). The pattern, Flame Wave Socks by Ann Budd, was really straightforward and easy to follow. The only change I made was I used size 4 needles throughout (instead of starting with 5 and then changing). The fit is just fine and maybe even a little loose on top.
If I were to use this pattern again, I would choose a solid color yarn. The mottled colorway makes it very hard to see the subtle wave pattern. Overall a good sock. I have never used a stretch yarn before and wasn't sure how tight to pull it while knitting. I think I could have pulled it a little tighter. Does anyone have advice on using a stretch yarn?