There is a presser foot for curves call the Curve Master. It is available several places; here is an Amazon link:
http://www.amazon.com/s/?ie=UTF8&key...l_8vbcpccewl_e
If you watch the youtube video demo it looks amazing. I bought one, but then I adopted a baby, and somehow haven't found time to test it (the foot, that is :-) . I hope you find something that works for you.
Darren