Goldilocks had to keep trying chairs and bowls of porridge repeatedly until she got the right one. Knitting socks is the same for me. I had to knit three pairs of socks for my husband until I got a pair that fit.
The first pair I made using Patons Kroy in Denim Jacquard were too small. So small that they are now my socks. The second pair knit with a thick gray marl wool, were too big. He uses them as foot warmers when camping out. And this third pair, knit with Lana Grossa Meilenweit Fun yarn, a wool/polyamid blend, fits just right.
I do wish I had used a lusher yarn, but now that I have the sizing right, the next pair should fit and be nice to the touch and eye.
Heel flaps were my downfall. First too short, then, too long and then just right. The heel flap effects the width of the gusset area.
On the second pair it was 4 inches. Robert has a very high instep so it actually wasn't that far off. But, 3 1/2 inches is just right.
In addition I've found that a more elastic cast on also helps, like the German twisted Cast On.
In regards to the color pattern, I don't know what my mother was thinking when she picked out this color scheme. It was one of four balls of yarn she brought back from Germany this past spring. It's actually the most attractive one. The yarn has a stiff, rough touch. It's also very thin. Too thin for cushy socks to wear in big winter boots. The socks are thin, like dress socks, but those colors aren't dress up colors.
In any case, I'll record the exact measurements for future Robert socks and pick to a super comfy yarn. In regards to a better color, Robert says he'd love a pair in fire engine red. So be it.