I'm not sure, but it seems to me you need to tighten both bobbin and top tensions. I would use a testing sample of the same fabrics and thread to see if this helps.
The zigzag stitch is the one that tells you whether your tensions are adjusted properly. Imbalances that do not show up on a straight stitch will show up on a zigzag.
Edit: I also see that the issue is on the curve. Bobbin thread is pulled up on one side of the curve; top thread is pulled down on the other side of the curve. I am wondering if the thickness of your fabric/stabilizer combination plays into this....
On second thought, you need the gold thread to look perfect on the top, right? I think the solution is to loosen the top tension *slightly* and tighten the bobbin tension. That will allow the bobbin thread to consistently pull the top thread down, whether it is on an inside or outside curve. It doesn't matter if the top thread shows underneath.
Sorry for the rambling. Have not had enough coffee yet today.......
Last edited by Prism99; 09-25-2013 at 09:16 AM.