I started building SP 94635 G50-15 GS Gondola three maybe four years ago. I was interested in building one of the Detail Associated GS gon kits as it looked like an interesting kit but I wanted to use the flat plate ends for variety. As it turned out there was only one group I could model using the DA kit as the base, the SP's G50-15 class built in 1942 by Bethlehem Steel. This required several additions or changes of small details to do this class:
1.) scratch built Buffer Plates
2.) creating what I think are Jacking Pads at the bottom of the first and seventh side posts
3.) changing the shape of the tabs where the Sill Steps are attached
4.) creating accurate Sill Steps to mount on the Tabs
5.) creating the rectangular opening on the Tabs
6.) removing the styrene for mounting the ladders and installing separate grab irons and mounting bolts where ladders would have been
7.) used sheet brass to make the Top Corner gussets where the ends and sides meet.
I used the flat plate drop doors with small rectangles of lead glued to them on the underside. Lead is also between the twin center sill members giving the car about 2 ounces of weight.. I used Badger's Modelflex "Oxide Red" with Speedwitch decals that cover all of the SP's GS gon types. The car required repair at the TN&O's Shreveport, LA cars shops in 1953, requiring it to be reweighed there. Perhaps this occurred during its journey eastward carrying something for a customer in Tennessee.