I have the pattern at home, I'll try and remember to check the number of the pattern.
When I upsized mine (only had to go from a 42" to a 44") was add an inch on the seam on side under my arm and an inch on the body in the front directly below your chin down to your belly button. There is no seam here per se, you use the patern piece and put them back to back as if there would be a seam but cut it from 1 piece of materal. Also added 1 inch to each side of the back. This ended up being more then the 2 inches I needed but because I did the vest double thick and most of them were on seams it ends up with the vest just barely fitting. I will be redoing this now that I have a little more experience sewing.