Attaching front number plate

[Doive]

Been tidying up the front of our car, first off removing the daft sidelights from a trailer/caravan, that were presumably fitted to get it through it's first MoT in the UK. These were stuck on with sticky tab squares, so thankfully the bumper cover isn't marked. The number plate has been stuck on with four bits of velcro - which is good as it means no unsightly screw holes. When I take the car to shows I was planning to remove the number plate, and fit a dealer style plate in it's place, but I want to dispense with the velcro - I had wondered about having sticky backed magnetic strips on the plate. Is there anything metallic directly behind the bumper cover, or could I get up in there to stick a lump of metal in? Would I need to take the bumper cover off?

[Guinney1971]

from memory, there is no metal in the front fascia, but behind the fascia is a big foam impact
absorber, with a metal beam behind that.

Some cars had a 'US Spec' front licence plate holder that bolted to the the fascia - my
car had one when it came in from the USA - I'll post a couple of pictures - but obviously
that is designed for US sized licence plates, not UK ones.