All the comments I’ve made so far in this thread have been based on memory of a project I finished at least 25 years ago - and I don’t remember when was the last time I looked at a Revell Constitution outside its box. I know for sure that I applied the basswood planks over the plastic deck parts, and I think shaving those “pads” off the bottom of the deck parts lowered the deck so the 1/32"-thick planks brought it level with the waterways. But I could well be mistaken - and it’s entirely possible (though it hardly seems likely) that the thickness of the deck sections is different in more recent moldings of the kit. I certainly don’t recommend that anybody working on such a project now be guided by my recollections of something I did 25 years ago.
I’m also pretty firm in my recollection that I used Bluejacket britannia metal deadeyes on that old model. And that made a world of difference to the appearance of the finished product. I think I also made a set of scale parrels for it, using plastic sheet and glass beads. (The big Revell kits are better in that respect than the Heller ones. The Revell designers at least understood that yards need to be fastened to masts.) I honestly don’t remember whether I replaced all the plastic blocks or not. My budget was such that I may not have; I certainly would if (gawd forbid) I were doing it now. The Revell blocks actually aren’t so bad, if one interprets them as having rope strops. A thoroughly, authentically-rigged model of a frigate should, of course, have far more sizes of blocks than the two included in the kit - and the smallest ones should be considerably smaller than the smallest included in the kit.
As for LEDs, I probably used some primitive, layman’s terminology when descrbing them earlier in this thread. To me, “burning out” is what happens when a light bulb (e.g., a traditional “grain of wheat” bulb, like the one I built into my Revell Constitution, and three out of the four full-sized lightbulbs that are in the light fixture in the room where I’m typing this) gets old and tired. When too high a voltage gets applied to a light bulb or an LED, it, in my vocabulary, doesn’t burn out; it BLOWS out - a far more spectacular and memorable phenomenon. On my Young America I wired up the LEDs in series with little resistors (which came in the same package), and I’ve never run them on anything but a 9-volt dry cell battery. As I understand it, an LED won’t burn out unless it’s subjected to some sort of abuse. But I think it’s always a good idea to make any sort of electrical gadget accessible in the finished model.
When it comes to making decks, my gut reaction is to avoid trying to shape any sheet of any material - styrene, plywood, or anything else - into a compound curve - which is what the surface of a sailing warship’s deck is. (It curves up at the bow and stern due to the ship’s sheer, and up at the centerline due to the camber.) In most cases the easiest way to handle the problem is the way the shipwrights did: make the deck out of individual planks, laid over individual beams with the camber cut into them. That’s what I did on my little model of H.M.S. Bounty, which is also based on a Revell plastic kit: http://www.hmsvictoryscalemodels.be/JohnTilleyBounty/index.html . I made a series of deck beams out of basswood and pinned them down over a copy of the deck plan, with the forward and after beams shimmed up to match the sheer. Then I glued the planks down to the beams. I don’t remember exactly how I attached the beams to the inside of the plastic hull, but I don’t recall that it was particularly difficult. The Revell 1/96 Constitution is at least twice as big, and needs to have two planked decks. But I imagine some similar technique would work.
Another approach, similar to what I did with my Young America, is to make a “sub-deck” out of wider strips (say 1/2" wide and 1/32" thick) of basswood. Such strips are narrow enough to work with conviently without being forced into compound curves. The joints in the sub-deck don’t need to be particularly neat, and their location doesn’t make any difference. Once you have a smooth wood surface to work with, laying the planks is easy - and the layer of adhesive between the planks and the sub-deck will actually make the finished structure stonger.
The question of humidity, vis-a-vis plastic and wood, is interesting. It seems like it could reasonably be expected to be a problem. All I can say is that I’ve got two models, the Bounty and the Hancock, that have extensive amounts of styrene and various kinds of wood in them (along with metal, silk thread, brass, copper, britannia metal, and probably several other substances that I’ve forgotten). I finished the Bounty in (I think) 1979, and the Hancock in either 1983 or 1984. They’ve been through three changes of residence and experienced some pretty extreme humidity changes (Ohio, Tidewater Virginia, and North Carolina are like that) - and the Hancock’s hull, which is hollowed-out-solid basswood with styrene exterior planking, made a trip across the Atlantic and back by air in a suitcase. So far neither of them shows any sign of damage due to environmental changes. (Frankly I’m surprised that none of the rigging has gone slack, but it hasn’t.) Again, though, it’s worth noting that these are pretty small models. A 3-foot long one might experience things differently.