I removed my rear valence same as the shown, then welded a steel strip to the inside of both bumper mounts.
Trimmed the ends of the rear panel so it fits neatly against the wing beading when lined up.
Cut away all the double skinned part on the underside of the panel and with a trim here and there it fits exactly,
if it wasn't for the 4 Dzus fasteners holding it in place you wouldn't really notice it's removable.
You can just see it in the picture and make out the fasteners.