Maniac - Just curious why do you need 2 machines to quilt a quilt? Does one do something special that the other does not or do you just like one better for piecing and the other for quilting or something? I use the same Bernina for all phases of my quilting and it works just fine. I'm wondering what I'm missing.
As for the issue at hand, I think the questions many have asked are great questions. I always use either cotton or 80/20 batting because the poly will shift too much. And yes, the biggest problem might be the drag of the quilt if it is not properly supported. I finally invested in a good table where my sewing machine actually sits flush with the bed of the machine and it has made all the difference for that reason. Of course where there's a will there's a way so I used to put extra tables (little tray tables work pretty well) all around my area to support my quilt at the back and on the left of my quilting area. You would be surprised how much difference some of these ideas mentioned will help you. Try them all until you figure out what works. Then happy quilting!