that is big thread and a small needle. I would chose a larger needle, 16 or even 18 for a size 30 thread. But I would also move to a thinner thread. I use a Size 50 and a size 16 topstitch needle, and it works fine for me. Even if I had a 30 or 40 on top, I would always have a 50 in the bobbin. Play with these different combinations and your FMQ stitchich should improve. Of course all of these changes will demand you tweak the upper AND bobbin tensions. Good luck.