I've started recommissioning my Rapide and upon removing the brake light switch it appears to be open to the elements. I see from the parts diagrams it's missing a backplate but is there also a gasket for this or should I just use some gasket sealer to try and reduce moisture ingress? Or would it be better without any gasket or sealer to aid moisture draining because as far as I can see it's inevitably going to allow moisture in?