Truss-rod & Bolster configurations on OR&L Passenger cars

I've been studying many photos of Oahu Railway coaches, surviving and deceased, for clues as to sort out the truss-rod and bolster details.

So far, I've learned a few things.

The shop built clerestory coaches (such as my kit) had the customary two truss-rods which connected to truss-rod irons at or just before the bolsters. The body bolsters were the common type, metal plates, presumably attached to the side sill (I have yet to find a photo showing the bolster-side sill arrangement for these).

The arched roof cars, as well as shop-built clerestory combine #36, and the observation cars Pearl (Carter built) and #64 had wood body-bolsters with truss-rod washers. The body truss-rods ran from end sill to end sill with square washers visible. #64 has more than two truss-rods...probably 4...which is peculiar for a car that never need to haul much weight nor have other cars behind it.

I haven't yet come to any conclusions about the Carter built coaches (3, 11, & 12) and combines (38 & 39).

I'm going to ponder these questions, perhaps ask around, and try to make sense of it. My gut says that the truss-rods connected to the end sills were a sufficiently stronger/better arrangement that they could get away with wood bolsters.

In the past week my preferred local hobby shop as moved out from under its former toy store roof (Johnny's) and become a stand alone store: Tim's Trains & Hobbies. Today, my friend Pat and I visited. I picked up a number of sizes of styrene needed for building Oahu Railway freight cars. In general, Oahu Railway freight cars used sills of twice the size of South Park cars (for which my "lumber yard" was stocked). Afterwards, we stopped by an open house at the local RR Museum (a collection of private cars in poor repair) and toured ubiquitous Cascade as well as a 10-1-2. For those not familiar with Pullman cars, Cascades were sleeping cars built by Pullman starting in 1938 with 10 Roomettes (single rooms) and 5 double rooms. A 10-1-2 was a heavyweight sleeper (1920-1935).