You have gotten some great advice here. Just to add-put it aside and try something smaller first. Support the quilt. Also, try a different stitch for the SITD. I've used a serpentine, fagotting stitch or even a zigzag. It makes it easier than a straight stitch and looks neat too. Leah Day's site is the best and there are other great sites and videos to watch. I've also tried the QAYG and quilting in sections. It works good too. One more thing, I just finished a twin on my DM-it was the largest I've done and I got one pucker on the back. After I washed it I couldn't find it! Practice too!