How difficult it is depends on the throat space and also what batting you are using. I have done a very large king using warm and natural batting on a machine with a 9.5 inch throat. A bit hairy in the center of the quilt but fine once I was out from the center a little. Supporting the quilt and having an extended table is part of the secret. You want as large a flat surface at the base of the needle as possible. For support, I work in a corner of the room, so the quilt can't slip off the left or back of my desk/table. I use my lap to support in front if there is more than will fit on the front of the table. It does take a bit of muscle to work a large quilt through the machine, so frequent breaks are a good idea.