My opinion on a starting place is somewhere within the helmet and chest. Its good to work from the core out because you can work everything out very proportionally. The collar armor can help a lot in lining things up.
I'm sorry, when I saw the words 'Jack Sparrow' I just had to say it, I am TeamFett's friend that is amking a Jack Sparrow costume, and we will fight in the hallways and record it for all to see... lol