OK, this may be a really dumb question, and it may have been addressed in the prior 66 pages (which I admit I have not read all of), so here goes anyways...
Once you glue the top hull to bottom hull (per the instructions) it appears that one would be hard pressed to see any of the detail in the back room, unless you keep hatch door open and then maybe you'll get a slight peak.
When I test-fit pressing the two hull pieces together, there is a slight gap along the engine pylons seam...so if you decided NOT to glue the hulls, I imagine this seam will always be readily apparent.
I think back to the Polar Lights Jupiter II with the lower deck -- I ended up not building the lower deck because it is rare enough that I lift off the top shell to even see the full upper deck...and I'm thinking that if I end up gluing the Proteus hull together (to avoid the gap in the engines) there is a fat chance anyone will ever see the back room...so why even build it (the back room interior)?
Now, I am also not lighting mine or getting any photo-etched pieces, etc etc -- pretty much just gonna build it straight from the box...so maybe those with plans to go all out have some other trick up their sleeve as to how they will showcase the back room.
That said, I would be curious for those pimping their Proteus out, how do you plan to show off your interior?