I wish I could say that the Stefano was significantly lighter than a hardbound sketchbook, as reducing the weight of my bag was the initial motivation for getting it, but it's only an ounce or two lighter. It's less bulky, though, so it feels like less. I wish it were a little lighter, but it has so many other benefits that I use it every day, even when I'm not traveling.
The watercolor tin attaches to the leather cover with what used to be a desk nameplate from a former corporate job I had. But I've also made one with a 6-inch plastic ruler. Anything flat, thin and stiff will do. This blog post shows the assembly: