Jim, What do you think about using the teflon Magic Bobbin Washers with the L bobbins? I got some for FM work --they are supposed to eliminate backlash & bird's nests on back of quilt. Haven't used them yet though.
I would avoid using the type L bobbins, as they are too short for the
12000. Yes, they work, but they will start bouncing around as they get
low. It would be better to wind them off onto a Janome bobbin. Janome
bobbins are class 15, which is equivalent to size A.