Whilst thinking over the aforementioned fit problems, it occurred to me that all the bad-fitting bulkheads came from the same parts sheet, page 6. So, to test this, I dropped in bulkhead G, which is from a different sheet. Ta-daaa! Fits perfectly.
In contrast, bulkhead F is too large. Here, I'm pinching the fuselage skin tightly to the lower bulkhead, and there is not enough skin left to wrap the bulkhead completely, even though the bulkhead has been substantially sanded.
Not only that, but bulkhead E (also from page 6) is also too large, and since the cockpit floor fits bulkhead E perfectly, that would seem to indicate that all the cockpit parts are too large as well. Guess which page they came from? That's right...page 6.
I referred this problem over to Chris, who will hopefully relay it over to Marek for prompt treatment. Can't say I'm enthused about having to rebuild the cockpit, though. :( Oh, well. If we didn't have such difficulties, we would have fewer stories to tell!
Cheers!