Even a fairly deep groove in a drum doesn't necessarily compromise the stopping power, as long as the overall diameter isn't way oversize. If a drum can be cleaned up over most of its width with a relatively moderate oversize, leaving a groove or two doesn't present much of a problem. On those Huck brakes, matching the radius of the shoe to the drum is important. That can be done by gluing a piece of coarse sandpaper to the inside of the drum and scuffing the shoe into full contact and then removing the sandpaper. Using a water-soluble glue like wallpaper paste makes it easier to remove the sandpaper when you're finished fitting the linings to the drum.
Jerry
