I have noticed that the horizontal cuts in my parts are real rough and cuts that are vertical or angled away from horizontal are near perfect.
Is this a known behavior or do I have something wrong in my set up? My frame is 15 degrees off of vertical. I was thinking that it might need to be on more of an angle.
It sounds to me like maybe what is going on is that the tension in the belts is too high up there and they could be fighting each other. You can play around with the simulator here for your frame size and see if that matches up with what you are seeing: