Tight colorwork

I've been working on the Winter (The Wind Can Be Still) socks by Oakwood Knits. I am a rather tight knitter so I went up a size, and also knit inside out to help keep the floats loose. Even still, I can't get the socks over my heel. I plan to make all four seasons of these socks and I want at least one pair to fit! How do you keep your floats loose? I am already planning to go up a needle size for the next pair.