What size quilt are you planning to work on?
I had a Viking Lily that did a fantastic job with FMQ. I believe the harp size would have been about the same as the Interlude. I just shoved the quilt through and puddled the part I was working on around the needle. Granted it's a tight squeeze with a queen size quilt, but it can be done.
10 years ago, larger harps were not as common as they are now. Some fantastic quilts were made on machines with harps no bigger than yours - where there is a will, there is a way.
Janet