I have a number of machines and I have tested fmq both ways, with feed dogs up or down. For vintage machines and even antique machines (100 years old or more), where feed dogs don't drop, I find I can do very good fmq by using a Stoppax attachment and having the feed dogs up and uncovered. This even works on treadles. I normally find them on e-bay for about $60. I don't see any there now. They are about 50-60 years old and made in Denmark, I think.