Sounds like you are in an ideal location there Matt. The lathe would not happen to be a 3D CNC equipped one? You chould really make some cool stuff with one of those. The mast base looks good. What boat is it going on?
So many people start counting money when doing things themself, and end up not building anything as they can make more money by working an extra job or some overtime. Refreshing to see what you are turning out!

Welding gases are quite seriuous stuff. I did a welding class once, and the teachers was quite insistent on what we could weld and positioning of the ventilators.
Perhaps somebody on the forum knows more about welding stainless and what the risks are..