Started weighting my Weaver 40' tank cars, actually so far not hard, however the first one I did was an old 48 footer I picked up used twenty-five years ago. I think someone glued all the detail on and I couldn't get it apart. I drilled a small hole in the top underneath the fill cap, dropped in some lead shot and decided to pour white glue in there so the shot wouldn't move around and to add more weight. Not a good idea, glue started leaking out in several places above the trucks. looks like it finally stopped oozing out, I'll wait till it dries and see what happens. Delrin trucks so hopefully the glue will come off.
Clem