Worked with the Spectre boot / shoe model a bit by isolating the mesh and playing around with it in Pepakura. I measured out my leg and scaled the model accordingly, I noticed that the model of the boot itself is a little on the small side but the height seems to be fairly good. Printed the pep files for one side (right leg) onto 110lb card stock, cut out the pieces, and taped everything together.
The sizing issue was confirmed in that the boot is quite small--I want to be able to mask over a real shoe with the finished pep piece so I'll have to splice a few inches of length into the piece later on. The model otherwise seems to be pretty nice. It's a single unit as it stands and therefore doesn't have any articulation in the ankle at all. I plan to separate the shoe section from the shin bit so that I can hopefully walk freely. There is some concern in that during walking, as the ankle rotates, the 2 pieces might grind into each other and destroy themselves. Hopefully everything will mesh well enough that there won't be a problem, we'll see.
I'll have to make the other leg and then add fiberglass to stiffen up the piece and go from there.