Hi, I will try to explain it.
The 66 series flats were originally built as standard gauge stock cars and are over nine feet wide. This made the 662(8?) much to wide to clear the giant Redwoods and Doug Fir for which Roaring camp is so famous. At times these trees are right next to the tracks.So close infact that if you are firing, you better keep your head inside the cab! For the Roaring Camp crews, it was much easier to trim off a few inches of the stake pockets than moving the railroad or the trees. As it is this car just clears with no room to spare.
Phil