Right, these hoppers were designed to be full of coal at 70,000 lbs (80,000 lbs with height extensions).
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www.spikesys.com]
When those hoppers were used to transport ganister rock to the brick mfrs. in Mt. Union, they were often found to be overloaded. It was apparently enough of an issue that the EBT built a few shorter 2-bay hoppers specifically for rock service, rated at 60,000 lbs:
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www.spikesys.com]
These are also shorter than the first-generation 2-bay hoppers.
I don't recall seeing a picture of more than 3 or 4 loaded hoppers being handled at once on the 4% NARCo branch.