That rule of S sounds familiar And by the time I'm ready to bind the quilt, I too have that feeling that the worst is over now!
I can't really think of any larger space that I could use, but my living room is just big enough to baste a quilt this size, if I push some furniture to the side of the room. I've moved my desk away from the wall so there's space for the quilt to hang down at the back.
Renting time on a long arm or having someone quilt it on a long arm is probably the best solution, but it's so expensive that I can't really afford to do that on a regular basis. For a real heirloom quilt it would definitely be worth the money though, it looks gorgeous. So far I've mostly hand quilted larger projects but I'm starting to appreciate the look of machine quilting more and more.