When I do diagonal lines on a quilt, I use blue painter's tape and follow that to get straight lines. Tonight I started to SID on a baby quilt and I decided to use the blue tape as a guide along the seam. I also reduced the speed on my machine and it turned out much better than it usually does. I realize that using the tape might not work on a twin-size quilt but thought I'd mention it anyway. My SID looks better than it ever did before. So hang in there...it will get better.