Hi there does any one know if its really nessasary to have 2 warning signs for spain ? I will be travelling through France Spain and Portugal. I dont think its compulsary in France but is in Spain. I have a Peugeot Boxer with right off set bike rack on the back door which i will have 2 bikes on. The bikes spead across the whole width of the back of the van door. I read some where that it was necessary to have 2 warning signes , one at either end of the bike? Seems like over kill? When ever I have seen photos of them people seem to just have one in the middle? Also is it really necessary that they are aluminium?