Try relaxing the quilt top a little in the frame. I use Aurifil 50 wt. on my Janome 6500 that I use as a sit down to quilt on. I found setting my machine to mode two and not dropping the feed dogs works better then dropping the feed dogs. I use a top stitch needle 90/14 Schmetz. From what I understand the 1600p is the same as the 6500 only without the bells and whistles.