So my Tail Tidy on my 2011 STR lost a bunch of weight but the number plate, which are pretty small in NZ since we went away from the squarish ones, did flap around a bit.
Either way it was noticed that the plastic was starting to split. Early into a 2500km trip around the South Island. Fortunately I got back with it in place. I took it all off and with a cardboard template made a thin sheet steel brace out of some chromated side of a large server, but could be any steel you find. There are ridges on plastic but I ignore those, then just bolt it all back together.
I'll post a pic when I'm on my phone later.