I've embroidered on the front and back of several onesies. I take out one side seam, I use a sticky stabilizer on the inside and a water soluable stabilizer on the top so the stitches don't sink into the knit, I rarely hoop anything that stretches. After I do the embroidery I remove as much as the sticky as possible and iron on a layer of the soft stabilizer so what touches the baby is soft.