I have to agree with Ben... this subject is really complex. Just look
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at the span of 25 years in your list -- I'm sure that besides length &
capacity there must have been other differences.
I'm starting to understand what vendors are up against -- there must
be 100 different design permutations for 2 bay offset hoppers!
"Here is a list outside of Illinois Central that had the "short taper/chisel side" twin offsets
B&LE 50001-50750, 10 panel, blt 1949
CofG 21500-21699, 10 panel, blt 1949
C&IM 6000-6349, 8 panel, blt 1949
CCC&StL 74065-75478, 8 panel, blt 1926-27
CCC&StL 88000-88999, 8 panel, blt 1926-27
DL&W 83300-83799, 8 panel, blt 1934
DL&W 85000-85499, 8 panel, blt 1940
D&M 5000-5024, 8 panel, blt 1948
EJ&E 40000-41699, 12 panel, blt 1940
GN 73200-73699, 8 panel, blt 1931
KGBW 401-420, 8 panel, blt 1948
HCTX 9901-9960, 8 panel, blt 1937
L&M 1000-1299, 10 panel, blt 1949
MC 11700-11755, 8 panel, blt 1924-27
NYC 450000-450994, 8 panel, blt 1924-27
NYC 451000-454097, 8 panel, blt 1924-27
NYC 450010-450988, 8 panel, blt 1924-27
NYC 451084-454296, 8 panel, blt 1924-27
P&LE 3350-3399, 8 panel, blt 1924-27
There are too many more classes of NYC & P&LE cars to list here
P&E 2801-2950, 8 panel, blt 1949
Not so fast, my friend. When discussing hoppers, do not go by appearance alone. You have to take dimensions into account, notably IL and height of top chord above rail as they contribute to the overall appearance of a cut of hoppers. For example, as David Thompson pointed out, the NYC System cars are dimensionally similar to the USRA twin, with IL of 30 ft 6 in/height of top chord above rail 10 ft 11 in (actually taller than the USRA twin), while the IC cars had an IL of 33 ft/height of top chord above rail 10 ft 8 in. To put the difference in length into context, put a Tichy or Accurail USRA twin hopper next to an Athearn twin hopper.
If you drill down into the other cars, you'd find more differences; for example, the DL&W cars had an IL of 34 ft, and you mixed in 40 ft cars, which further muddies your analysis.