None of this stuff is necessary on our cars. The rear sway bar would help, but the DDM brace is a better design for our application. The Sonic's chassis is already so rigid that I get a wheel off the ground leaving some parking lots (driving gently), and that's on stock suspension + DDM rear brace. The short wheelbase is part of that, but it's also a rigid design in general, probably the hatchback more than the sedan.
Additionally, as someone mentioned earlier, there's no triangulation in any of the designs. The front and rear braces rely entirely on the strength of the perpendicular welds and the torsional rigidity of some relatively small tubes for strength.
I'm sure Ultra Racing builds its products well, but these parts are just for show. They might be good mounting points if anyone wanted to put skid plates or a full belly pan on their car for an aero or rally build, but otherwise if you're not worried about what the bottom of your car looks like, I wouldn't bother with these.