Rust repair at rear trailing arm connection plate area.

[Fiatracertracer]

I am trying to repair a pretty bad rust spot at the passenger side rear trailing arm connection right behind the seat.

I am looking for ideas from people who have experienced repairing this area and how they did it.

I have been doing pretty good with the mig welder on simpler areas of the floor boards and my welds have improved over time .... but how do you repair this area?

Any help would be greatly appreciated.