I'm glad you guys like the project.

The most effective change that I've noticed is the amount of the metal that melts from the stick and thus the thickness of the weld bead.
As far as I know, with DC current, electrons move more easily from the stick to the base metal.

To nova_robotics:
I am willing to try this hint of yours, do you think the welder (cables especially) would stand that higher current? 30 Amps more don't seem too much for the cables, actually.

To Christophe Mineau:
Sure you can put it externally. Since the output coil it's directly connected to the cables I guess you want to mount it right before the cables to avoid the soldiering part and stuff, right?

To Frank S:
What were the results, what change did you see in the welding?