I have both the red and the natural; I mostly use the natural since the red did discolor my soap once.
The only time I've gotten pock marks was when I cpop'd a bit too warm; otherwise it has not been an issue (my normal technique is to preheat the oven on "warm" a few minutes, then turn it off, put the soap in, and put/leave the oven light on until the soap is firm enough to cut. It's usually still warm at that time).
I too used the cardboard box for support for quite a while (a year?) and it worked great. Eventually my DH made a simple scrap-wood support frame and now I use that. I still have the boxes "just in case" (of what, I don't know)! But I gotta say, girlishcharm, your box is amazing clean for being 2 years old! You're a cleaner soaper than I am!