Just one other thing to take into account when strapping things, usually not a problem with shorter beds, but frame flex can bite you in the **** on longer frame flat trailers with straps ( and chains too but usually once you've gone through a retension on a chain, they'll keep everything under tension).
Only time I ever lost anything off a truck on over 1.5 million miles was off a42 ft flatbed , had a pallet of rolled roofing with a couple of tarps strapped to it and took a left turn up a steep hill and the frame flex twisted the straps around and ripped the binding around the rolls apart and it all went bouncing off onto the sidewalk.
I pulled off into a church parking lot and the guy behind me in a little truck pulled in and said , hop in I'll give you a hand ( Small town Arkansas ), and we get back around the block and there was some guy loading one of my tarps into his van ( definitely NOT a local boy
Put a stop to that real quick.