I have recently spent countless hours scraping the rubberized undercoating from the bottom of my 72 monte carlo. The floorpans and frame have all been sand blasted. What can be used in lieu of the rubberized undercoating? I have been looking at por 15 chassis black semi gloss. Also por 15 metal mask for the rearend and suspension parts. Does anyone have any experience with these products? any help would be appreciated. I want the bottom of the car to look immaculate. thanks