Then obviously she can’t use the wood pieces for blocking the wheels. I have not used any U-Haul trailers for a long time to know they were metal floored.
With one less holding point, this makes it even more important that she anchors her load down with suitable binding products like chain and chain binders. No one ties down farm equipment with rachet straps. Look at other trailers with equipment on them, utility workers, construction trailers, the rental store, and machine loads on the road. They are ALL chained down to the trailer. These folks move machinery daily, have to have a professional attitude in tying it down safely before heading off with load in traffic.
We had one flatbed trailer with a trencher on it tip over while making a corner because the road culvert gave way under the wheels. Machine STAYED ON TRAILER, in place on the tipped trailer laying on it’s side. They had to get a big wrecker to pull trailer back onto wheels, to move it again. Machine stayed in place thru the entire process, which did make things easier to get upright again. Driver got a DOT commendation for his well-secured load after accident investigation was completed…
You want your load tied down that good.
OP might want to reread the labels of rachets she bought, then return them. I have never seen breaking strength be larger than working load strength. Maybe there is some new magic out there in straps, I just have not heard of it. Breaking point is what I call the jerk point, sudden jerk is where a product breaks. Like emergency braking stop from road speed as someone pulls out in front of you. Often breaking strength is less than half the working load strength. I DO read those labels on breaking and working strengths to prevent “accidents” happening.
Check the load strength on carabiner too if you want to use them. Most are pretty cheap, low strength rating. Too often they just pull apart with stress of load when you NEED to depend on them. I would not use them hauling machinery.
Hoping OP has a safe trip with her new spreader.