Thanks, Bob...that is the general idea, but cut that height in half. Basically, I have a 36" high smoked plexi dropboard in a wooden grooved "frame" throughbolted to the steel pilothouse itself. Above that is an excellent Atkins & Hoyle sliding hatch that is fully "doggable" and is in heavy-duty sliding grooves.
The sliding hatch is padlocked over the dropboard top flange. You either would have to boot in the dropboard or snap off the padlock to gain entry.
The "sill" is about two inches. My aft deck is pretty high...I can't say I've ever have even a splash from a following sea there...but that's in Lake Ontario, where getting pooped is usually a function of not seeing the squall line crawling up your stern.
What I want to get is basically two gasketed aluminum panels, both doggable from the inside and lockable from the outside. The lower panel can be solid, and the upper panel can have either a fixed or an opening ventilation port, maybe 5 x 12 or so, with heavy glass. The idea is that the lower half, when dogged, makes for a "bridge deck" of 20 inches, while the upper part can be latched open, with the dogged hatch keeping all but horizontal rain out. This will allow ventilation and communication in moderately heavy weather, but also will allow a quick way to seal the pilothouse far better than present. Even fully shut, in a capsize, we would take on water. A well made gasketed and horizontally split door would lessen water ingress significantly, and would make the boat a more daunting target for burglars in port.
In the picture above, you can see the saloon companionway. I also want the ability to close that with gasketed aluminum panels, as well as a similar "downstairs" to the aft cabin. The pilothouse has internal scuppers, believe it or not, so that if I gasket the engine room hatch, and shut those doors, I could take about a foot of sea water in the pilothouse itself before the electrics suffered...
Thank you for the link. You've given me something to think about.