I free motion quilted a large queen quilt on my Bernina 400 QE with a throat (harp) of 7.5 and the height is 4.5.
This year I did stitch in the ditch on my featherweight on a queen sized quilt. (The batt was not too thick.) The featherweight has a throat space of 5 inches by 4 inches high. Why did I do that? To see if I could; to brag about it. LOL After I stitched in the ditch on both sides of all the sashing, I used my Bernina to FMQ each block.