Mystery Stole 3--the Swatch

I've decided to try the whole Mystery Stole thing next month.
Here's my swatch:

Yarn: Misti Alpaca
Needles: size 4
Blocked Size: 4"x4"
I actually knit 2 swatches. The first one had a mistake on the last row and I didn't like the cast off so I tried again. In the second I alternated slipping one knitwise(column 1 & 3) and purlwise (column 2). Unless the pattern specifies, I never know which is the default one so I wanted to compare them.
My biggest problem so far is my cast off--I think it's still too tight. I even cast off with bigger needles and it was still tight. I may have to bring out the "table leg" 35s, seriously. Any tips would be appreciated, because I can't tell you how mad I'll be if I do the whole stole and the cast off ruins it.
Comments
And what size cast-off needle did you use? "They" always say go up a needle size but I never could get the cast-off loose enough for toe-up socks. Until I learned ez's sewn cast-off. But I've also recently figured out that if I knit a sock on a 1.5us (2.5 mm) needle and I cast off on a size 7us, it works for me. Yes, up that many sizes. Get out the broom sticks.