Frank,
Yep. Originally, I only had two layers of carpet and even field point arrows went in all the way to the feathers.
So, I tried a 3rd layer. It stops everything about half way down the arrow shaft.
It must have something to do with the layering.
If I had a a 4th layer, I would put it on.
I don't know the density of the carpet, as I pulled it out of the trash. But, the denser the better.
Oh, because the carpet is layered vertically, the carpet dries quickly after a rain. No mold, or anything. Works pretty good for free!