Not quite the tail piece thread that seems to have been put out of it’s misery?
I discovered that my existing number plate for my XBSx was already on the legal minimum. Being a 7 digit plate it doesn’t look so cool with the cut down tail
, but there is hope given my re-use of the number plate end of the original cheese grater casting. This mounts the plate an inch lower than the typical cut down show plates l see on some XBs so the larger plate isn’t so stark. The L08 mini reflector is stuck on the back of R&G led lamp between the brake lamp and top of the plate. 
Looking at some custom plate providers like ‘Number 1 Plates’ gives some ideas on how to tone down standard plates by waisting or tapering the sides while maintaining legal spacing.
After reviewing some web sites, I hit on the idea of simply grinding an approx 15 mm radius to the four corners. This significantly tones down the visual impact of the plate. The inside and lower edge of the indicators are inline with the top and side of the number plate, but cleared by this radius, neat! I also filed a few mm off the straight edges just to steal a little more reduction.
