I think it actually turned out better that way... I'm always sceptical of films set in aircraft that have reams of corridors and trapdoors.
Several of us that worked on the L-1011 went to see Passenger 57 when it came out. We were amazed at how you can go from the wheel wheel, to the cargo compartment, to the cabin and that by connecting just two wires together you can dump fuel.
By the way there are several access panel in the floors of the L-1011 that lead to the cargo compartments, galley and mid electrical service center. However, if there are LD-3 's in the cargo compartment you would find the space between the top of the container and the bottom of the floor beam to be really tight.