|I found some knit fabrics can be fiddly at times, meaning the edges don't serge finish well, no matter the differential feed used on the serger or how taut you hold the knit fabric to serge.
I decided to try Sulky Solvy, the original, meaning the thin solvy not ultra for the seam edges. I placed a strip of Solvy underneath the knit fabric edge while serging. The serger feeddogs seem to grab the knit better with solvy underneath. This resulted in a nice even serge seam.
You can then spritz the seam to remove the solvy or sew up the knit garment and then wash it to remove the solvy leaving a nice seam finish.