David Weaver
The discussion of what amateurs often make as gar as mistakes go making planes reminds me of something george wilson told me years ago. That is, if you're not a good designer, you're far better off resorting to copying something good. It took me a while to figure that out.

I filed the back of the mouth on a Slater kit vertical years ago, and didn't realize until later that it needed to be filed forward. Other than that, I did a very good job. It was a panel plane, and I set the mouth at a hundredth and it still had tear out problems. That single issue made the plane substandard. I later filed it properly and sold it fully functional. The makers of those kits didn't have the sense to copy some of the elements from older planes quite right.