POR15, undercoat, or sprayon bedliner?

Not if you remove the problem then take good photos to show what was under there. The point of products like those is to preserve, so the same issues don't happen again. Better products than what the factory used to prevent rust. Yes, people sometimes use them to hide and deceive, but that is not proper use of the product.

that maybe true, but one's lack of patience and or skill's usually overide quality and doing things right. if it wasn't acid dipped or media blasted cut out and replaced and e-coated it probably didn't do it any good slopping por 15 over a scuffed up or wire wheeled floor did not take care of the rust, it still continues to grow underneath and it will find it' way.i've been restoring cars for years and have been presented many different option's and products that will take care of rust . but it still comes down to remove the cancer you can't put a band aid on it and say it's gone