I looked at it last night. Those are pretty good instructions. Especially for Instructables! When I was growing, we made our own chaps and spur straps, and as a knifemaker, I make some pretty basic sheaths. This would be an interesting project. I need to find a local source for leather, as well, since these shields are getting to the strappy stage.
Well, these are my first attempts. All made from plywood (which is basically what the Romans did, although I find a scutum REALLY uncomfortable to hold), covered with cotton cloth instead of linen (because I had an old bedsheet handy), and then lacquered before painting. Like the big viking shield, they'll get a rope rim covered in rawhide.
I'll do some research into the leather targe and see what I can find.