this is a good thread and i thought i would add a couple of perspectives from my experience having built several chesapeakes as well as the shearwater line and a handful of strip-built boats and being an avid kayaker for the last 20 years
first, my opinion on hatches. i like forward and rear hatches. they are practical for a number of reasons: 1) they provide convenient access to storage, 2) the provide access to otherwise closed areas to effect repair and help ensure the space inside is as expected (dry). 3) even if you don't use them often, the problem without them is you can't make them happen on the fly. 4) they also impact your construction approach... so in their absence, you need to think very carefully about how to change the build order, engineer for the appropriate stength in their absence, or deal with a place you will never see the inside of.
second, the relationship between hatches and bulkheads: if you have or want bulkheads, i think you should have a hatch. i think for reasons above, deck hatches are the most convenient. but closed areas, in my view, are a no-no. i just am not comfortable not being able to inspect a hull i am relying on. waiting to see a problem from the outside or hearing water slosh around where it shoudn't, in my view is simply too late. with respect to sea kayaks, i also want bulkheads to minimize the amount of water that can be taken on if you swamp or have a failed role. bulkheads are also important structural elements and you have to change the build/layup to add strength in the absence of bulkheads. the only kayaks you routinely see without fore or aft hatches are racing boats and whitewater kayaks or very short boats that don't need bulkheads for strength.
third, can a boat look good with a hatch? opinions may differ, but i think you can have a very good looking boat with a hatch and i have some kayaks where the hatch are flush and some that sit up on top...and some approaches that attach the hatch with toggles, some that use straps and some that are blind (attached with rigging from the inside). so its really never been an issue and is part of the whole deck layout and the look i am trying to get. so i can get a look that is very much like no hatches (flush and blind) if i want....its just a bit of effort.
can i build a boat without the hatches and add them afterwards: the chesapeake line has the hatches happen towards the end and you can, if you want, take it out for a spin before adding hatches. shearwaters typically set up their hatches prior to the deck and hull being attached becuase they want you to have access to do the inside taping through the hatches becuase they assume you will have bulkheads. also, the hatch structure of a shearwater would be challenging to do blind...but doable. generally i follow assembly order becuase its been worked out what the issues are....and going out of order means you have to do a lot of thinking to ensure you did not put yourself into a corner that you did not anticipate. interestingly , in most strip builts, becuase the decks are not tortured (bent over the bulkhead), bulkeads often go last after the hull and deck have been taped. a shearwater, unlike a chesapeake, can do bulkheads last as well as the deck really does not rely on the bulkhead for shape...just strength. but then it makes it a pain to put the bulkhead in after the hull and deck are together.
if i put a pin hole in the bulkhead, where would i put it? in the discussion above, its mentioned putting a small hole in the bulkhead to allow air to equalize. in my experience, this is a very good idea. it can get amazingly challenging to get a hatch off if there is no pressure equalization. however, i would put the hole in the middle of the bulkead (not at the top). the reason i suggest the middle is it allows the boat to be up to 1/2 full before any water would get in. when you take on water in a cockpit, however, remember that the boat is not always right side up....it might be upside down. so the middle of the bulkead is where i was always told by wise folks where to put it.
can you do an endpour without a hatch? endpours can always be predone before the hull and deck are attached if you put some material up in the ends and simply make it part of the assembly process. i typically do this to keep a boat light. however, if you really want to 'pour' your end pour....then you have to have access.
anyway, i hope this helps. lots of ways to skin a cat at this. hatch fan:)
h