I will tell you that perfectly balanced stitches are something to strive for, but not always achievable. This is why many long armers use the same color thread in the top and the bobbin. Also, if just a tiny bit of top thread is showing on the back, and the bobbin thread is not just laying on the surface, I would try washing the sample. If you use cotton batting, it shrinks a bit and minimizes the issue.
I don't have this machine, but have the 3 hole guide on mine. I was told to try skipping one of the guide holes.
And finally, this video is not for your machine (I don't have this brand either) but the process may help:
http://www.youtube.com/watch?v=Q1mRhcquZTM