Spoke too soon
Turns out there was an error in the tool path for the part I just cut out. When the center square cut out was done it cut on the outside of the line instead of the inside. Rather than scrap it I decided to cut a reducer and weld it in.
The part fitted really nice. All that was left was to weld the piece in.
After a quick buzz round with the welder and grinder, the problem was sorted.
Making the Axle Supports
Once again I took the peice from the 3D model, made a tool path and cut the piece out.
Another one of those and I can start welding parts together.