I don't slop seams together and hope for the best but I don't fret over a smidgen off. I just don't care and don't care if anyone else cares. I have good luck using Wonder Clips to hold the seams right where I want them when piecing. The clips are so much better then pins. No distortion of fabric and I don't have to remove them when sewing. The backs are flat so they glide along the machine bed.