Front bed not sealing

Our new/old 2001 3023 is in great shape for its age, but there is one thing that we can't quite figure out.

The front bed and the front shell has almost a 1 inch gap between them when it is opened and latched securely. The rubber cushion on the shell side (kind of a roll of rubber) looks like it might fill the gap if it is pushed down - but it won't stay down!

There's no flap to seal on the front end, so we just don't know what to do with it other than stuffing something in it after it's set up.

Any ideas?