For good measure, when you replace the carpet, that you remove and refinish any rusty areas before you put the new carpet/pad in.
We have used several rolls of jute padding for warranty repairs/concerns at work. it's the 3/8" thickness, I believe. What I was surprised at was how dirty and dusty it was, in that roll. Each of them has been that way, all the way to the middle. Might want to use some rubber gloves to keep the grit off of your hands. Might need to re-dress the cutting edges of your scissors, too?
Just some thoughts,
CBODY67