Thanks Mike...

There was a post a week or so ago stating that this "bracing" might be for nailing down the center Walk-Way from inside the gon.
As Mike has detailed so well here that the brace in difinately between the Center Sills (for lack of a better term).
If one has access to a kit or a model of one of these cars, close inspection will show that the blocks that, the center floor in nailed to, are on top of the Center Sills. I think those blocks are at least 4 inches tall so you would need at least 6 inch nails just to reach this center bracing. It shows that this is probably not the reason for adding this center bracing.
I think Mike's thoery of Bracing for the tremendous inpact of when the bottom doors were dropped out of these cars makes a great deal of sense. I was on a Freight Train Special back in 1991 when they dropped some ballast on the way back to Chama, those doors drop hard!
Thanks again Mike (And Dave Squire) for chasing down this rumor of the Center Bracing. I just sat back and egged them on.
Kevin Cook