I put the foam in there all at once and it expanded more than I expected so I had to trim a lot of it away. I think this led to all the pinhole leaks and frustration. So if you're going to try it I would recommend that you lay it down in several layers to build it up slowly.
I'm planning on it. I was hoping to be able to collect some moss and not have to pay for it, but that is a little hard to do in February in South Dakota, so I'll just go buy some soon.