I wouldnt mind seeing pictures of a striking file.
For holding sheet abrasives, I made some using decent hardwood. I just drilled a hole for the radius I wanted then cut through the middle of it with a band saw and left enough meat to form some sort of grip and way to steady the paper. They hold up for many years and dont scratch if it hits the work. For narrow spots, I use acrylic triangle stock for the backer. I consider them disposable, but they hold up good enough, and are easily cut to different lengths and reshaped as needed.
I have a few files that I ground off teeth to make safe files so they dont cut on one or two surfaces. The belt grinder will do it quickly, and keep them cool enough and pretty true.
