|I belong to a Serger Club and today we made knit t-shirts all on our sergers.
The instructor gave us a really good tip that I wanted to share.
On each side of the shoulder seams, fuse a 1/2" strip of Dreamweave fusible on the wrong side before you sew them together. You have to be careful to cut the dreamweave correctly. Cut the same direction as the selvage, but don't use the selvage as it's too hard. If you use this technique, your knit shoulders won't grow!
Hope this helps - I think it's a great little trick!