Why cedar? Some cedar is very soft. Screws can work loose easily. Dents and gouges would be common.
Wouldn't a harder wood more resistant to everyday use and abuse serve you better for interior
In our home I use cedar for closet linings and when making drawer sides. When left unfinished it provides a nice aroma and perhaps some moth and insect resistance. Finished it would loose this benefit and I wonder what other virtue it would have when used for a boat interior?
If cost is an issue, cherry, maple or butternut are less than half the cost of mahogany and would be excellent choices and provide a beautiful interior.