Lori, that is a great idea. I covered the hole behind the toilet with thick non treated wood to give Rainbow something to pick on. He is really bad on anything within his reach. Myrtle has done a job on my cabinets and door ways.
I took Pajarita's way and put metal on almost everything. It would have been a lot easier and cheaper to use your method. I will try it on my non protected places.
Sides of cabinets were being chewed on so my son screwed pieces of safe metal on them. The top of cabinet doors are more difficult. I set the v shaped metal on top of the cabinet doors. That works great. I just have to get used to them being there. Most of the time I forget and the metal falls to the floor.
You have a flying toddler. Even pedestrians do damage at their level. They know what I mean when I say "stop that" "get away from there" "fly". They listen but go right back to their work when I turn my head. They are pushing my buttons.