I have alot of trouble doing SITD on my long arm. You might need a ruler to help guide your foot. Also, just because a thread works on your Bernina, does not mean that your Mega quilter will like it as well. I would suggest, trying a new thread, trying a long arm ruler (diff than your cutting one, the quilting ones are thicker to accomodate the hopping foot), or just not doing SITD till you have had a chance to practice it elsewhere. Its a learning process! Take a deep breath...you WILL figure this out... Probably nothing you wanted to hear! Sorry!