I'd knit a bit before you decide. Knitting stretches and the ribbing may be intended to be a little tighter as ribbing usually is. Anyway, knit (inch maybe) a little then take it OFF the needles to try it on. Put a long piece of smooth, contrasting color yarn on a yarn needle and thread it through the stitches. For the body you can get a rough idea with using a really long cable or multiple cables. I prefer waste yarn though.
Is it this one? If not we need a name.
Actually that link is so not helpful as far as Ravelry because the projects go to multiple patterns. However, let us know if that's it or another.