Nice Box...
Just remember ...With Gas-less, Flux-Cored Wire... You have to run your MIG Welder on Straight Polarity... (DC - Electrode NEGATIVE) so you'll have to Switch the Positions of Your Leads ahead of time and set the Machine up as suggested in your Manual for FCAW:
This is Bob Moffatt...
an excellent Welding Instructor from Weld.com who is using 240VAC MIG Machine here below very similar to your Pro-Mig Welder while explaining, "The Basics of FCAW (Fluxed Core Arc Welding)" and de-bunking some of the Myths vs. the Advantages surrounding this choice over MIG Wire with an Argon-Carbon Di-Oxide Bottle Gas
(especially on Windy Days when you're outside ...and your Shielding Gas just gets "Blown Away"):
This Weld.com Instructor uses the very same 0.030" Flux-Cored Wire that you just bought
and shows Three More Tricks to help you out:
Some differences between GMAW vs, FCAW with Terminology and Procedural Differences:
One last suggestion on your choice of a Flat Steel Strap... Having it be at a 3/16" X 3" Thickness and Width would probably be better suited for replacing the Lost Structural Strength in the SUV Under-Framing and would be a Damned Side EZR for you to Weld on. Otherwise, you could also laminate the work with a Second Piece of 1/8" X 2.75" Steel Strap cut to Length and then Drilled out with 1/2" Centering Holes every 6" or so. Then just weld it in evenly around the perimeter inlay after fill welding in those holes on the Second Plate-Strap for additional holding strength. Finally, you can grind everything down smooth, making the edges radiused just before doing the last Metal Anti-Rust Treatment and Painting.