Can the hangar bay be used to store cargo? If so, how much?

Dimensions of the Hangar. It would be possible to install optional Cargo-locking plates to the Landing Bay and use some of the space for hauling. Overall, you'd be able to add roughly 4500 additional SCU of cargo to the ship if you used half of the available space in the Landing Bay (with the remaining space being used to enable a Cutlass to land/take-off with that cargo.)