Have not tried this but for an open boat I think I would just uses some heavy plastic sheeting. If you pull it tight and it doesn't assume the proper shape you will have the same problem with a heavy or stiff skin. Duct tape on the bow and stern seams should make it water tight enough so for a test. Maybe a little down the keel since that is the most likely place to damage it.

Again, I have not tried it but having done stretch wrap I would think t this would be much more durable.