I don't mean to sound like a jerk, but those welds in that picture don't look up to par for those feet. I'm sure it looks fine but if a collision occurs the shearing forces will rip those welds apart.
Are you using any shielding gases?
I don't see any well defined bead and that lends me to believe that proper penetration was not consistently achieved throughout the entire weld. Think of it like this, without a well defined bead your weld becomes more like perforated paper. Sure, in one instance its strong but apply shearing force and it'll rip right apart.