I borrowed a demo Sweet Sixteen and plan to buy it. Absolutely in love with it. My only problem is using rulers. I watched the video, but when I lay the ruler down, there is a bump where the machine meets the table - it's not a straight surface. The ruler doesn't seem to work well with it. Does anyone use this machine for stitch-in-the-ditch? Do you use the ruler, or just carefully run the foot along the seam line? I'm doing ok with FMQ, just need practice. But I need to do straight lines, too. Would one of those slider sheets help?