Well, I'll say it seems to be very well printed (which cannot always be taken for granted). You also say it tracks really well too, which implies--at least to me--that it's hollow, or keeps the weight low. All good.
As far as the print design itself, I'll point out only a couple improvements I might want to see: Thinner gauge strapping, and (perhaps) a strapping which conforms to the outer radius of the most upper pipe. Something which curves along the outside of the corner pipes, rather than "square out" at a right angle. Of course that assumes straps might not run outside a hard, 90 degree block too, and I'm out of my depth there. I can only guess how a load like that might be blocked at the corners--or not.
Beyond that, the only other thing I would suggest would be to attach cables to keep the whole pipe-load centered. In this case they would probably run over the top of the load and down to the stake pockets along the sides of the flatcar, in much the same way you see cables running over the outside of lumber loads stacked along center-beam cars.
As far as actually printing and getting it out there? I can only applaud. I have two 3D printers, both still unpacked, and so I have yet to print a single thing myself. So I'm happy to see it working for you.
You may or may not know we DO have a 3D printing thread here at these forums too, and a couple or three or four guys who are also cranking out prints. I would point you at it, but I can't find it at this late hour.
You will find it if you look. And more power to you. Good stuff!
