Good for you for investing in the blue bobbin case.
Did you also get the free motion quilting feet package?
If not, too is well worth the investment.
The 6600 and those two additions was what got me hooked on FMQing!!
At the time, I was hesitant in spending the $, but put trust and faith in my dealer and went with it ... and never looked back!
ENJOY your 6600 ... a great machine!