One of the chronic Bugeye rust areas is the forward portion of the rocker panel. It would seem that road contaminates thrown off the front wheel batter this part of the car, and accelerate corrosion. The passenger side seems to take the brunt of it because of the crown of the road, which, of course, causes water and salt to gather on the curb side where the right front tire can throw it up.
The car pictured here is one we are preparing for a repaint. It features this exact kind of rust-through on the passenger side, and it is fortunately contained on just the outer skin of the rocker. You can see the box of the passenger footwell (inner sill) is still intact. You can also see the bondo on the back side of the piece we cut away, evidence of a former repair.
Kenny does an artful job cutting away the outer skin, and grafting the front portion onto the balance of the rocker. The result is impressive, and now strong and sealed for many years to come.