The throat space on the machines is really going to limit you. the 401 and 500 series machines don't do great FMQ because of the drop in bobbin and raised plates. I don't like my 401 for FMQ, but love it for other uses. The 66 or 301 may be the best bets. I love to FMQ on my 301. But, since you've spent so much on a frame I'd look into a larger harp space machine. Just my 3 cents worth:>