And the final detail. I didn't want to get away from the fact that this craft is supposed to manouver in space as well as well as land troops on planets. I took two hubcaps (really just hole covers for ork artillary wheels) and after trimming them a bit I glued them in the space between the spine storm bolters. In my mind they are used to attach to air-locks and allow Space Marines to enter craft that they interdict in orbit. I'm sure the crew also uses them to go out for a bit of fresh air too!