Some "European perspective" as some have called it, though some would prefer it to be posted in the "towing or hauling something wrong" thread
I needed a pair of wheels for my bale trailer, which i couldnt get anywhere because the machinery wreckers in my area sold a truckload full of their used tires to Poland. So i bought an old single axle Claas selfloading hay wagon, built 1983, of which the owner already used the sideboards for something else.
To get this all on my trailer, we cut the axle bolts loose and cut the frame right behind the intake. Because a 3 ton manure spreader weighs 800kg, i estimated this hay wagon would weigh 1500kg.
It turned out to be a little heavier, because the mans small excavator couldnt lift it on the stick, we had to hook the strap around the main boom.
On the highway on-ramps i would lose speed in 5th gear, but otherwise the 2.5 TDI hung in at 1700rpm and 90kmh pretty neat. We got it home safe, with no instability issues at all. Last week i loaded bricks for my BIL, and after getting home i calculated that i had more than a cubic meter of wet concrete on it, which is 5.5-6k pounds net, and probably 7 to 7.5k gross. My guess is that this load was near the same weight.
This was the 2nd heavy load on this trailer after i rebuilt it, which consisted of lengthening it, and making a new V towbar of 2x4 inch tube, from the first axle all the way to the tow ball, lowering it by 5 inches and putting low profile 195/50R13 tires under it. Because this trailer is quite wide, it has the same trackwidth as trucks, so it never wanders in and out of dipped truck lanes.
I will save all the chains and sprockets as well as the heavy angle gearboxes for future use, as well as the cutting blades to use as weld-on wearparts, and maybe use the floor for my manure spreader, which has a rotten floor and a worn out conveyor chain. Then the rest will move on to the scrap trader, which will get me about 15 ct per kg nowadays.