Yes, the bar on the M1082 trailer is about 3/8" smaller in diameter than the one on the trucks. Makes sense, since it weighs less. I should have the mold done for those soon (in the coming weeks).
I just haven't gotten to the uppers yet. Honestly, this all started because my lower bushings were gone, and good replacements were unavailable. It's all time and money after that. It probably took me 40 hours of work (e.g. design, fabricating the master pattern, making the mold, etc.) to get from idea to a finished bushing. On top of that, it cost several hundred dollars (even considering that I own lots of the expensive equipment needed, such as vacuum pumps, vacuum chambers, pressure casting chambers, 3D printers, CNC mill, etc.).
Doing the uppers also means I would need measurements, so either disassembling my truck (which isn't broke), or buying a bushing just to get measurements. Ultimately, I did do that, and paid like $50 for an upper bushing to get measurements off of, so I have that now. I made a CAD model from that, and next will be designing the master patterns (which are different than just the CAD model of the bushing, because it has to take into account what tools will fabricate it, such as 3D printer bed size and orientation, as well as how the mold of it will get made, such as pour spouts). This is all true of any of the other bushings people want... upper and lower cab mounts, etc.