I’m just finishing up a museum model of a Ti-class ultra-large crude carrier, currently the largest ships in the world at 441,585 deadweight tons and displacing 509,484 long tons at full load. This is the Ti Oceania. It is painted completely in flat white, as the ships colors, markings and activities will be projected onto it by 3D projectors.
In real life, it is 380 m long or 1246.75 feet, with a beam of 68 m or 223 feet and a draught of 80 feet. The model is 2.375 m long or 7 feet 9 inches, and 0.425 m wide or nearly 17 inches. The hull is MDF, medium density fiberboard, so the model weighs over 100 pounds.
Many of the details were drawn in 2D for photo-etched brass, or modeled in 3D for 3D printing. Other details such as lifeboats were mastered, then molded in RTV silicon and cast in resin.
Some retired ultra large crude carriers were a bit larger, but I’ve never heard of them being modeled in N scale. As ULCCs are actually shrinking these days, this may be the largest N scale ship built for a long time.