Just wanted to update this thread for anyone that might need this information in the future
The Individual Vehichle approval inspections manual (for cars)says:
For markings to be considered 'indelible' they should be unlikely to become disfigured or obliterated during the life of the vehicle. Whilst stamping or engraving is preferable it is possible to accept a printed or painted plate providing it has been treated in such a way that it is most unlikely that essential information would be obliterated ordefaced during the normal life of the vehicle.
The Stamped in VIN must be marked on the chassis, frame or other similar structure which is not easily removable
The Stamped in VIN must be placed in a clearly visible and accessible position by a method such as hammering, stamping, etching (metal chassis) or embossed, moulded into the structure (glass fibre or carbon fibre chassis) so that it cannot be obliterated or deteriorate.
while the says Motorcycle single vehicle approval manual says:
in an accessible position and readily legible, the required vehicle identification number by a method such as hammering or stamping, in such a way that it cannot be obliterated or deteriorate