You might want to consider using a split batting technique. I have done this for large quilts on my domestic machine. Basically you layer backing and batting as usual, but then cut the batting into thirds (being sure to make registration marks on the batting so you can put it back together exactly as it was -- I used a permanent Sharpie pen for this). Add the top, and baste the quilt top with only the middle piece of batting in place. (I used basting spray). Quilt the middle section first, being sure to leave about 6" free on each side of the batting. When finished quilting the middle, peel back the top and insert one of the remaining batting thirds (you can use an iron-on fusible tape over the batting join, if you like), baste that section, and quilt.
Marti Michell describes this and other methods for making a large quilt manageable on a domestic machine in her book:
http://www.amazon.com/Marti-Michell-...dp/B0002J5GX0/ . I first ran across this technique in a Debra Wagner book (would have to pull them out to figure out which one).