You mean this pic?
I did have a bulkhead built with a hatch and all but when I got finised building the seats and control panels, I found that the gunners seat wouldn't fit with the canopy on the ship. If the canopy didn't have that brick connection the seat would fit. There is a giant cheat....when I put the canopy on, I lay down the gunners seat.
So, unfortunately, the bulkhead wouldn't fit where I wanted it to go (right behind the seat). There is also clear space from the rear of the cockpit to about where the thruster nozzles are that is tall enough for a fig to stand. That's how they board, under the tail. I had thought about doing an interior in that space but I got lazy and also really didn't have any ideas of what to do other than a couple of cells and/or a bench and maybe a small vehicle.