This is probably a pretty basic question, but I'm frustrated and wanted some help/words of wisdom/etc. I'm working on the relaxed cardigan from 'Modern Classics' by Louisa Harding. I'm using the yarn called for, Fauve, since I found a beautiful green color on sale. The recommended needle is 10.5, but I "thought" I got gauge on size 8's. I'm fine when I measure the width, but my gauge seems to be way off when I measure the length.
I tend to have this problem when I try to knit a sweater, and I know it keeps me from forging ahead with more complicated patterns. Should I go down a needle size, assuming that will take care of the length issue? And then should I increase the number of stitches cast on to account for the fact that my width will now be under gauge?
I would appreciate any help I can get, and I can take a picture of my work so far (I'm knitting the back, working on the increase section right before the armhole shaping).