There are a lot of ways to approach sealing, so feel free to ignore my advice.. however, this is based on my experience with radios like this and Super 33+ type seal jobs and the way they fail in adverse environments (I deal with salty environs so things go bad fast).
If you want to go bomb proof on this, you have to use mastic to completely seal the junction between the connector and the body. As water comes down the body of the radio it can linger in the junction between the connector and the aluminum body and you will get corrosion over the long run. Usually aluminum oxide starts to build up underneath the white powder coat in this region and then progresses to a larger area. Also no parts of the N-connector should be exposed to water passing over it. A any water that moves down the exposed part of the connector can be collected in the perfect cup that has been created by your lower seal and over time this may propagate further down the sealed area. -PK
