Those socks look great!
I just learned stranded knitting in the form of Latvian mittens, and my teacher mentioned that the strands in the back shouldn't be longer than 3 stitches. It was a challenge in places where I had to use 3 colors, though, so I did fudge it to 4 or so sometimes. Longer than that would have caught in the back. Hope that helps.
On the needles:
Hooded sweaters for DD1 and DD2