Pretty hard to judge fitment issues regarding a larger screw and the relationship to the bracket. If the new screw cut thread into the bracket, it may be OK.
The problem that I would foresee is that the bracket bears a lot of torque and bending moment while in use and the part function is critical to keeping something together while the vehicle is in motion. Failure of the screw and consequent detachment of the bracket causing a bar to come dislodged and fly off/dragged is a risk I wouldn't take. In fact, if the screw breaks from just attaching, it's probably a poor fastening system to start. Could you remove the self-trapper and use a through bolt? Maybe a grade six or better bolt would be a better solution.
Good luck with your WDH.
