I'm at the point on my cardiagan where I'm sewing the side seams together - the long seams from the wrist to the waist. How long should the pieces of yarn be that I use for sewing? I managed to use one long piece to attach the sleeves, but I don't think I could keep one long enough to do the whole side seam untangled. Is there a standard length? On a side note, this is the first time I've used the mattress stitch and I LOVE it!