Thanks, that works!
However, we're getting into duplicates now. Karmarepair posted that same document in post #8, and I realize in looking through my OneNote notebook that I've gotten the Timbren "rubber block" axle-less suspension twice now, as well.
Pretty sure that's for inter-state commerce; the big commercial tractor-trailer rigs. As Vigilant1 notes, for non-commercial trailers I believe that each state has its own rules for motor vehicles. There are certainly some federal rules as well but, as is overall, states have priority where federal law doesn't apply.
IF you were to go with rubber block suspension (that as a trailer builder I strongly reccommend AGAINST!!!) Timbren is leagues above Dexter (who, BTW, own almost every axle manufacturer in this market). Rather than start kludging up shock mounts, take a look at their tandem walking beam if you want a simple bolt-on solution with FAR MORE TRAVEL than any other OTC "trailer" axle.
Timbren Silent Ride Tandem Axle Truck Suspensions - Suspension for Trailers ANY single axle rubber based suspension is going to be VERY stiff and count on internal friction for some dampening. Again, if you want decent ride, you need air - but OTC air are for much heavier loads. Piece of cake to build something from small air bags though.
The simplest thing you could imagine was the old VW type I shown earlier) but that was for something around 1k lbs. not 2k. It is made from a "T" shape of two pieces of flat bar and can simply be cut, two more pieces splice in and welded back together to get whatever width you want without much fuss about alignment - but at 2K far too light. 2 of them would work, but you are back to the same problem as trailer suspension - old school adjusting bearings, seals, etc. and wheel/tire sizes getting hard to support. Also, as I mentioned earlier, brakes a good thing for highway, but since you are going only a few miles, not worth the bother at 2k.
As for regs; there are CMVSS and USMVSS federal standards in Canada and USA that apply to trailers. They "divide" similar to the trucking world at 26,000 lbs. and below that are nearly unknown and unenforced. As you have concluded, each state and province has their own take that easily pass USMVSS since those standards barely exist. For example: there is NO braking performance standard for U/26 trailers in the US, so NATM and its more ethical members build to and advertise a CMVSS standard that DOES exist (but is marginal at best....laughable if you have any understanding of motor vehicle safety). Side note: there IS an SAE committee studying this question/bigproblem, but they are years away from publishing anything (that will normally be adopted by Feds).