Yesterday's shoe pattern scaling fiasco has me questioning my math skills.

Have you tried printing a simple test square before committing to the full pattern? I started doing that after a similar mess with a scaled-up hat pattern... it turned out like a satellite dish. Now I always include a 1-inch reference box on my draft page and measure it with calipers. If that checks out, the scaling is usually sound. For orthopedic boots, you might even compare a scaled piece against a known object, like the sole of an existing shoe. It’s a boring step, but it beats ending up with leather large enough to reupholster a couch...