A couple more things that might help. From the ends of the tubing you are getting over penetration. You really should be getting just a little penetration. There is NO merit in having too much penetration. If you get any penetration, and it's consistent, that's all you need. I recommend turning your arc force UP to about 3 o clock position for best operation. This will affect the bead and sound of the unit. It will be a little more raspy, but it will lay out a flatter bead and wet in better. With what you are doing you could get away with 16.5 volts and about 185-195 on the wire speed.