I'd be a little suspect of putting much weight into a bag mounted to what is supposed to be a soft luggage stay.
There's a reason quality racks are not cheap. They are robust, and engineered to carry a reasonable load. I've seen the H+B setup on a new bonnie, it is very well done, and the resulting look with the black cases is as close to period correct as you'll find.
IMO, pelican cases on a street bike are like a plywood spoiler on a porsche. As always, YMMV.