How would one go about altering a infant vet pattern that is 0-3 months to 3-6 months. The pattern is using sc sdec and revsc and it is done in one piece with the shoulders being sewn. The link is below of the vest that I am interested in altering,

Saddle Tramp Vest-Free Crochet Pattern | Cobblerscabin's Weblog

Thank you in advance.

Robyn