If I want to substitute a yarn that gets one extra stitch to an inch than the yarn called for in the pattern, should I putz around with needles to get gauge or just adjust the pattern sizing a little? Could I make the size smaller (It’s a two inch difference in the chest measurement.)
Personally, I do the simplest thing, so instead of fiddling with math (which I abhor!) I would fiddle with the needle size!
I’d go with needle size, too, since you can check the gauge on that and know if it’ll be right. There’s no way of knowing what an incorrect needle and different size will get you.
Save yourself a lot of trouble and just adjust the needles…