You know, I'd fiddled around with making the docking port a slight larger diameter than the collar to give it some wiggle room (like in the movie), but when I retracted the doors into the bulkheads, gaps out into space appeared at the top and bottoms of the collar which would cause dangerous decompression. Unless I restricted them opening to less than 3 feet wide and we clearly see them open more than that when Kirk and Scotty board the travel pod from the orbital office in TMP. The fact of the matter is that the screen-used model pieces of the travel pod and docking port were not constructed to be workable, so I had to take some license here and divert from screen-accuracy a bit to make a believable (and safe) docking port system.
Extrudable/retractable gaskets surrounding the docking port doors and filling in any detected gaps before the doors open to prevent decompression. They're there, but unseen.
