I just got busted for a homade junction box cover.It was a master peice we used the old panel as a junction box to the new service panel(only branch circuits inside).But the panel had square holes when you opened outer cover and it looked bad.So we cut a peice of 14 guage metal and made a nice looking cover that AHJ says won`t fly 110.21 But I can rivit 14guage to cover the existing holes and use the panel cover.Seems as if something could be waved in this situation.