Our own Dr Stears just published a beautiful set of 3/16" scale drawings of the 1909-1910 SUF boxcars in the just arrived NG&SL Gazette, Jan/Feb 2019, pages 50 and 51.
Bob's drawings show the as delivered cars prior to USSA hardware as well as in-service cars with both types of metal roofs.
Included is an underframe drawing (bottom view and cut away side elevations).
Thanks Bob
Jim Courtney
Poulsbo, WA