The TTA tank wagon was a tricky build, not least because of the limited selection of curved Lego elements. I settled on the 6-stud diameter cylinders (from the Lego City space launch centre). They were white and therefore required covering with an enormous "sticker", i.e. blank self-adhesive vinyl. The ladder detail was important to capture and I think I my implementation is a good first draft. The underframe also has pivoted bogies like the VDA and OBA wagons.
Its getting closer! New tender, new cab, new smoke deflectors, and more. Its now powered with a bogie in the tender--soon to be converted to DCC (hopefully!) Still lots to do, but I'm looking forward to applying the decals when she's finished.