I think what you are describing must be an old setup. The mid 90's Marstrøm model had no such thing, just four plastic pieces in the trunk keeping the board up or down.
The later models have a small piece of thin shock cord, about 5cm, secured to the board as a loop. This loop is slipped over a small button in front or back of the trunk to keep the board up or down. Very simple and clean.
On the late models I assume the bungee will break if you hit something. On the 90s models the friction is enough to keep the board up, or down. I think the small plastic strips are made of teflon, and the system works great (I have personally tested it) <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />