Another ITY fashion knit tunic top favourite of mine: I turned the neck edge over to the wrong side and simply cover hem stitched it down. It lies flat and looks professionally finished on both sides. Yes, you could use a twin needle if you must, but this still does not have the same stretch as a coverhem would so the stitches may pop at some point.
KNIT FABRICS: OPTIONS for BINDING NECK & ARMHOLE & HEM EDGES PART 1