Some say the stitch should be balanced, some say the top thread should show a little on the back. I do whatever it takes so the fabric doesn't tunnel. Using a stabilizer with thin fabric helps, even if it's just a piece of paper. I'm inclined to believe that the top thread is supposed to show a bit on the back because with embroidery machines where you have a lot of satin stitches and just dense stitching, you're supposed to have the top thread show 1/3 to 1/2 of the stitch on the back.
Cari