I can see that you are in earnest and that you know far more than I. Still, I have a suggestion. Rather than searching for the official value of this important parameter, how about adopting an empirical approach? Using the good offices of this forum, a suitable E34 could be located. I would certainly make mine available. Then a person of known weight could be asked to stand at the bow, transom or next to the chainplates. A measurement of the change in flotation level would not be hard, I think.Stefan stability and trim charts tell you how the vessel will trim adding weight fore or aft of the center of floatation ....
The three Lewmar deck hatches have vent positions which I always used, both summer and uncovered north country snowy winter. They proved adequate for unattended ventilation. Onboard I preferred to use a hatch tent over the forward hatch during inclement weather at anchor or at the dock. Underway, conditions dictate what can be open.also, noticed no deck dorades. How is this boat vented when underway or unattended on a mooring ?