Elden Gatwood wrote:

All interested should also be aware that the DA dome is pretty "fat",
representing a 2% dome for a large capacity car. This is NOT the dome
for that 8k or 6k car you've been working on. Remember, that 2% volume
(and hence, dome diameter and height) applies to the capacity of the
car, and the Athearn car is a whopper.

As my feeble memory recalls, the SP O-50-13's were 12,500 gallons capacity.
And yes, they were built by GATC, I believe in the early-to-mid 1940's. I
don't know if GATC made a Type 30 of that size; I'm sure Richard will know.
Somewhere at home I have partial copies of the erection drawings for three
different classes of SP tank car, showing the domes and their measurements.
I'll try and dig those out and look at the height and diameter figures.

Shawn Beckert