I driven my 55.2 for the last 15 years without a plate, and have never been stopped for not having it.
Some states require two plates, and some don't. It isn't high on the list of offenses to stop someone though.
If you're concerned about rust on holes drilled in a chrome apron, just put some RTV in the hole before installing the screws in the holes. Wipe it off close to the screws before it sets and it'll last for years.
