I sort of get it.
I also seem to be having trouble controlling three layers of fabric and keeping them in place, no matter how much I pin and spray. My machine seems to be having trouble stitching through three layers of fabric (espessily when I get towards the middle)...I got it set on a 4.5 and in some places it looks like it was set on 1 (very small stitches). It just doesn't want to pull the quilt through very well.
The only thing that I can think of might make things easier is if I sewed the top to the batting and then the back to that. That way I wouldn't have to fight like crazy to keep three layers from slipping...I'd only have to work with two layers (I guess once the batting and top are sewn together its more like one layer rather than two). At least in theory it would make things easier. What do you think?