I modified the factory "bike rack" so I have good points to strap my Yeti cooler, a propane tank and my generator, generator not shown in pic below but I took everything to work and customized it to fit perfectly.
If you don't have a "factory" rack, there is a lot of talk on the forum about adding to the frames / bumpers and creating issues if it was not originally designed to haul a load but a lot have done it by hiring a certified welder and adding bracing.
On my trailer it looks like they just welded some rectangular tubing to the frame rails and mounted the rack mounts off of the top of that and claimed 450 lb. capacity, I can get you some better pics of the way it is attached this weekend if you want them.