Besides my Sapphire I also have a Baby Lock Jane on an Imperial frame. Jane is a strait stitch with the 9 in throat. It has a primitive threading system with many steps. I run out of bobbin thread in about 2 rows of quilting and it is also difficult to use since it is a metal bobbin holder under the machine. I did buy a stitch regulator for it and I like that very much but havnt perfected it yet with the speed adjustment as it skips stitchs sometimes if I move to fast.
You can only do a very narrow row of quilting with this kind of system so it is limiting. I mark my quilt with a 4inch ruler to be sure I dont run out of room.