I had a real dilemma trying to figure out how to do the neck, I wanted to put elastic in it but I wasn't sure how to do it,because the knit it was not very stable, very unravely. So first I used a wonderful product called wash away wonder tape Here.
The Wonder tape was the exact width of the elastic I wanted to use, so I literally just put the tape on around the neck, where I wanted the elastic at clipping as I went.
Peal off the backing.
Apply the elastic.
Serge the neck and turn under.
It worked, and I am so glad, because I have several other pieces to make tops out of like this...