To be fair, the S-1/3 series are 40 feet, 6 inches long, from pilot to pilot. The S-1/3 measures 22 feet even, center-cup to center-cup centerline. It also measures 9 feet, 3 inches from both center-cup centerlines, to the pilot, at each end.
The S-2/4 measures 41 feet, 6 inches, from pilot to pilot. The S-2/4 series are 22 feet, 6 inches long, from center-cup to center-cup centerline. The S-2/4 has a centerline center-cup, to front pilot measurement of 9 feet, 9 inches. the rear measures 9 feet, 3 inches, centerline of center-cup, to pilot.
This means there is a 6 inch longer section, between the center-cups, on the S-2/4 series, and an extra 6 inch overhang, from the front center-cup centerline, to the pilot face. The 6 inches in the middle, not noticeable. The 6 inches missing from the front, is passable IF the models aren't actually longer, in the nose. All I have here, are S-2's, so no way to measure a S-1, to compare.
This measurement is so small, it's not going to be an issue, unless you are a "rivet counter'. The detail, for the money, makes this seem insignificant, compared to the price of brass. Just a thought, although the P2K stuff might be off, as well. (IF the Atlas stuff is off) As part of a group of close to 300 locos, and counting, I doubt ANYONE would catch the missing inches, considering the overwhelming size of the almost complete HO LVRR diesel roster.........