Pictures might not show you much.
I have a piece of 5 inch C channel fit over the rear cross member. It does not fit flush but snugs up with about half an inch left before it contacts the rear face of the cross member. (This creates a nice box effect too

)It is welded full length, top and bottom all the way from the two longitudinal frame rails.
I have a piece of half inch plate laid flush against the rear face of the cross member outboard of there. Again, fully welded
The bumper is fully weled to these pieces with through bolts for the Pintle and reinforcing of the cross member in this area also. I have 3/8 inch thick tabs which extend forward from the bumper alongside the frame rails about 10 inches and are welded completely.
I took this overkill approach after the weight on the racks and the leverage of the extended pintle that I was using with a low/heavy trailer, tore the back of the bumper loose from it's original mounting tabs to the frame rails and bent the rear cross member.
The bumper and it's mounting is now bullet virtually proof.

But... under much too vigorous rallying with a full load on the rack, I snapped the spindles holding the swing arms.
The assembly worked fine for several years with 40 gallons of fuel on the back
but increasing it to 60 and tossing a few more tools on the top that I have been carrying before pushed it past the limit for the smaller spindles I was using.
I will be installing heavier duty spindles (these were only 1 tons) and I will not be carrying as much weight on the rack.
It makes more sense to load the fuel between the axles and lower... so... in built in tanks. The rack will be used for everything else BUT fuel
I do not carry a spare. With tires this large it is problematic to say the least. Instead I carry everything I need to repair a tire. (Stitch up a torn sidewall or whatever may be called for.) I am seriously considering moving to 1400x20 XLs under this rig, since it sees little road time any more and I have other rigs that are much better for running roads and trails together, leaving this one for use only on the long distance trails that we are seeing more and more of. Since the XLs of this size can be run with 0psi under a '40... well

no more tire concerns at all... IF I could damage one
Actually... I WILL try the 1400x20s. The question is if I will stick with them
Mark...