It would - very roughly - be in the indicated area. But I wouldn't worry about it since you've pretty much got it for a vessel this size. Like I said, it's the deepest part of the superstructure, right in the middle of the ship.
But right now would be the best time to add superstructure detail, before it gets covered up by bigger details and railings (which will go on very last). All vessels have hatches in order to facilitate access - all ships would be useless without them, and crews would look very silly with no means to be able to actually get inside their vessels. Life preservers and other gear go on this time too.
Unfortunately it's hard to figure out all the detail that needs to go on a ship of any size or complexity, and you may find yourself going back constantly to add these in, even after the "final" details have already been added. This is a headache, yes, and unfortunately the best indicator of what needs to go on is to simply look at similar ships. But, I can give a few rough guides - for example, you have a funnel, but engines need to breathe too, which means air intakes. On a ship like this, they would basically look like grille or other meshwork that you would tack onto the side of the ship in some fashion, in a place that makes sense (i.e., water won't get inside and it won't interfere with something else). You could even slap them on the side of the funnel; or you can slap them on at the very back of the existing superstructure. Alternatively, you can add on additional superstructure, such as immediately aft of the funnel, or on top of the aft of the existing superstructure, to specifically accommodate the intakes. On a ship like this, boats would be optional, but something to think about. Also, inflatable rafts (they're the white boxy things - look up the Epicnopolis thread in Alt Universe for more details).
If any details come to mind, I'll mention them as they, well, come to mind.
Also DO NOT, I REPEAT DO NOT USE THE PICTURE I JUST POSTED. I saved it as a .JPG as a matter of personal convenience, as I was merely demonstrating where the C&C would be to answer your question. Hopefully this is obvious enough, but I've learned to never make that assumption especially on these boards....