I have a large rigid plastic suitcase on the rack, complete with inner tube round the 'weatherproof' seal, extended brake light and more importantly two locking surfboard straps which are steel reinforced. So all the valuable stuff is in the case and stays dry too.
Inside, behind the seats we put squashy bags, wet weather gear (just on the off chance)and other coats, etc.
Obviously travel as light as possible but we've never had much of a problem doing that in exchange for being in a Morgan. PS too old for surf boarding, just a lucky internet find!
