Needed rear case for helmet and backrest. Not much support on fairing mount. Made support bracket out of 1/8 flat stock mounting to rear antler bolt and top two bolts near seat. Welded on mounting bolts for Emigo case mount. Really strong support for case. Removable hardware takes few minutes to remove. Pics are not perfect but get idea. Don't pick on my welds using cheap stick welder. Grind and painted black.

I just made a 1/2" thick cast ally bracket/plate that bolts to the 4 holes that the OEM rack bolts to.
My top-case bracket bolts to that and has been heavily loaded many times over the years with no problems apart from the occasional wheelie when very heavily overloaded. Doesn't need any additional support as the rear sub-frame is more than strong enough.