67Monaco
Old Man with a Hat
Are these scalers safe to use on inside of body panels(rear 1/4 panels) to remove undercoating?
NO. It will dimple the hell out of the panel. It does to floor panels too but generally most people don't care since no one really ever sees the bottom of the car.
I found for undercoating that was somewhat pliable, WD-40 was the best. I have about an 1/8 layer of it on the entire trunk floor. I don't know what her grandfather was thinking but I bought a gallon of wd40, and use spray bottles to apply it. I went out and soaked about a 1ft by 1ft section for about 3 days applying a spritz everyday so it would stay moist. By day 3 the undercoating was scraped off the metal with a putty knife like cake frosting. I was so soft and pliable. Another spritz and wipe down with a towel to get the remaining goo.