Diagnostics please

I use the Judie Wise basic sock pattern for my socks including her recipe on gauging. My first couple of socks came out fine size wise. The last two too big. I talked to Judie about it over the weekend. Part of the problem with the bike socks is the cotton content, cotton knits/ribs flatter. She also told me to maybe subtract an inch from my ball of foot measurement rather than the 3/4" in the math. I am also thinking that if I am between cast on counts for 2x2 ribbing (let's say 66), I'll go to the lower number (64 to cast on) rather than the higher (68) Next time I guess. What do you think?