My intermediate trailer has no proper tie down points at all. Its a two axle flat bed between the wheel wells with a welded rail. I typically find myself either hooking into the top rail, or the bottom of the vertical supports for the rail. Looks like two 5000lb axles. I think the heaviest thing it has hauled is a few modern compact sedans, Ranger pickup, 42 GPW, and I think my dad hauled my JD3320 with it once or twice. In between I used it to bring the Hurco KMB1 back from Hemet, Ca when I bought it.
I've debated welding something on the bed for ages, but the outside ring of the bed is just 1/8 in x 2 angle. Modern weld on D-rings seem like brutal overkill for the applications.
In my various searches for cool tools I ran across these things.