From my (brief) reading that type of ships is just a cheat to cut canal costs (Suez) built for a short period till the rules changed.
It makes an interesting ships (why not do a real life version as well ?
) but not sure you should base your entire MM on it unless you are charged to go through the Bosporus ?
The Turret ship is it was known was built by Doxford, Great Britain, who had developed the type from an American whale-back type, mainly used on the Great Lakes (42 ships, boats, built between 1887 to 1898). The Turret ships were indeed built to cut on Suez Canal transit costs (which at the time were calculated on the basis of the weather deck area, hence the smaller area of the upper deck). Incidentally the turret shape had the added bonus of contributing some strength to the hull. The biggest user of Turret ships was the Clan line (IMHO), with British India also a big user. A shipping line which was trading east of Suez, but didn't use the type was Alfred Holt (Blue Funnel Line).
As for real life ships I have plans for several ships
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Thank you Kim for the crest
"Never fear to try on something new. Remember that the Titanic was built by professionals, and the Ark by an amateur"