===deck armor ===
As for the opposing armors...I believe the vessels operate in a slightly different threat regieme. Would the Dutch actually know SATSUMA's deck armors? I suspect that is why most countries simply designed with thier own known performance parameters in mind.
The old Dutch BCs have 80mm deck armor, the 30,000t DeRutyers have 125mm, the new 38,000t Utrechts have 150mm. The Dutch traditionally over armor, they would assume the opposing ships would have equal or less armor.
Class Est Comp Replacement Deck
Fuso ~1918 1938 50mm- Public
Nagato ~1920 1940 65mm- Public
Tai'pei 1928 1948 100mm- Not public. Presume close to DeRutyer, 120mm
Babur ~1912 1932 won't be a factor
Akbar ~1927 1947 100mm- Not public. Presume close to DeRutyer, 120mm
Shah Jahan ~1932 1952 30k Not public. Presume close to DeRutyer, 120mm, perhaps closer to contempary Utrecht 140mm ?
As such a mild difference in deck penetration could indeed be viewed as useful.
A rebuild ZP would
have to stay in service until ~1953!!! That new 10 year extension is really the burr in the reconstruction. A brand new build would only have to stay in until 1954 or so. However the Taipei, Akbar, and Shah classes will all be in service for most of that time. Furthe the treaty may well expire, or that 10 year clause rolled back. It is reasonable to expect that a rebuilt 36cm ZP would be effective for at least 10, if not 15+ years against a substantial portion of the enemy battleline.
===36/40===
As for the 36/40- as I said it was a toy. Actualy I think I built it as the first step in an effort to figure out what deck armor a 26k ship may need. However it planted the seeds that acceptable deck performance was possible in that range. It's not the final version. I'd like a little faster and a little heavier. But the 766kg shells already wouldn't fit under Rock's rule of thumb.
I just felt that before going out and trying multiple iterations of the gun(s) with differing calibers and shell wieghts and designing a follow on to Isjelsijk to carry them,
I should find out if I can upgun the ZPs to carry such things and just how heavy I can make the shells. a basic question still not answered. At this point, I'm inclined to use S&G as the model and simply declare I can mount up to twin 381mm as that's the only OTL comparison available.
I do realise a slow shell would have increased Accuracy problems, a quick comparison of the /40 and /50 showed a 30knt vessel would have moved about 400' at the 21500m range due to speed differences. The question is if the reduced accuracy is worth the chance to actually do critical damage.
One idea that intrigued me was to do something like the USN did- provide tables for two different powder charges. As I recall, for the Iowa's 16"/50 page they had a reduced charge meant for longer ranges to penetrate decks. I was thinking I had that from NavWeaps, but it doesn't appear so- though they do note
Like the Mark 5, the Mark 8 APC projectiles were designed for use against Japanese ships ("Plan Orange") at long range in the Pacific Ocean by firing them at a lower muzzle velocity and at a higher gun elevation, which allowed a steeper angle of fall to further enhance deck armor penetration.
but that's not quite the citation I was thinking of, but probably speaks to the same issue.
=====Mixed Calibers=====
As for the mixture of shells, how is 345mm, 360mm and 381mm any worse than the current 280, 310, 345 and 381, or the WW1 RN's 305mm, 343 and 381? Or the USN's 12", 14" and 16"- esp when the 16" for the Iowa would not fit the hoists for the 16" for the Colorado, nor the Alaska's 12" fit the Arkansas.
Further, when replacing the Ijelsijks I will likely mount 360mm not 345mm anyhow. Frankly, shrinking the number of shell types from 4 to 3 is not a concern. The Dutch certainly have the cargo handling skills that figuring out where which shell goes will not be a problem.
===Okun =========
Off Topic:. Nathan Okun's formulas are more correct, but I believe they are also more correct than those the Navies of the era knew. I probably shouldn't rely on them as they constitute hindsight. Perhaps if when/if we sim combat they should come in as the 'real' vs expected. RAM used BigGun for earlier Dutch weapons, so I figure continuing it is reasonable.
Oh, and thanks for the site link, I've used the facehard tables for a bit, but never tried using the formulas proper, the site looks to make that a great deal easier.