The only thing stopping the arm will be the brake light switch arm. If that weren't there, the pedal arm would simply bash into the toeboard. Eventually, taking your foot off of the brake pedal time after time will beat up the switch arm and the paint on the toeboard.
It'll eventually wear a hole in the toeboard. My cab was sagged enough that the brake switch arm wore into the toeboard, which was another hole I needed to weld up.
