"They were completely different hulls. The Sargos were smaller and about 100 tons lighter and their screws/shaft set ups were much different.. Sargos had 8 torpedo tubes and the Gatos had 10."
Sorry, Brother, I gotta disagree. The Gatos were only a couple of feet longer and less them a hundred tons heavier. The hull shape was similar and the hull diameters were identical. As far as extending the superstructure all the way aft, no biggie. In fact, with the Trumpy set up, a saw and some plastic stock, it would be simple in concept, if not easy in execution.
As for the torpedo tube count, he wants to do a diorama. That's a water line model, only two torpedo tubes (fore and aft) show.
But all of this is moot, since he wants to do "Tigerfish", from "Operation Petticoat". "Tigerfish" was played by USS Balao (SS-285). Yankee Model Works has Balao, in 1:350.
"In fact the Gatos and Balaos were much different too.. I.E. Steel decks vs Teak decks etc."
Gotta take exception here, too.
The teak decks continued right up thru the Tenchs. The steel decks came with the Guppys. The biggest difference between the Gatos and Balaos was the hull thickness. Remember, we called the Balaos "Hundred Fathom" boats? The rest was cosmetic, and differed more from boat to boat, than between classes. Especially after a couple of yard periods.
DBF,
Mike K.