I am doing a queen size FMQ and its not easy true but I am still not believing that I am actually doing it. WOW I am making a music quilt for my DD and its been a chore but the results are still over amazing to my own eyes. So many have complimented me on this own design quilt that I still can't believe I can do this.
So answer to your question. Yes you can quilt any size by machine if you really have the patience and time.