Air bladder leak on the top fitting of bag. Cannot access Savannah model

[sailor]

How do you access the fitting on top of the air bladder. There is a piece of channel going across. I removed the 2 bolts on either side, but it really does not want to move. The floor above is a sheet of aluminum. Thought about cutting, but don't feel that should be necessary. The line seems to be plastic. I am sure this is original. I also have another problem that I will start another thread for. Thanks for any help. This unit is pristine original. No rust anywhere.