I completely wore out the front end of my 95 F250 4x4 8800 GVWR because the 95 Vanguard slide in camper we had at the time , loaded up with me and my family weighed in at 11200 pounds.
2400 pounds overweight, handled and braked well and the PSD did not hardly know the camper was on.
We did a trip down to South Cal, weighed it on a Cat scale. I thought I might be a little over my GVWR, 2400 lb was way over my comfort rating , we drove a lot slower on the way home, sold that camper and went back to a fifthwheel.
Shortly after that, my steering wheel stayed 1/4 turn from normal position, I heard a clunk going around corners. I brought it in, the swivel bracket, a main component of the Ford 4x4 IFS
was broken off in one corner, holes egg shaped, 2 bolts missing out of 4
The truck steered well, it was low mileage, had done very little 4x4 off road and the front end was wore out. I got it fixed under warranty. It was a big bill.
On tire pressure, always when loaded , have your rear tires at max. Mine are always at 80 PSI with the fifth wheels. When I had Slide in campers and knew I was over my GVWR , I ran them at 90 PSI. I got this from a tire web site that stated when running tires at their max weight rating, it is OK to go 10 over max. This was 10 years ago. Maybe this advice is no longer current. Anyway, I ran 90 and never had problems.
On any weight rating, the weakest component, sets the rating.
My SRW 2005 F350 has a 7000 lb rear axle. to get that rating the tires would have to be at least
rated for 3500 lb. In fact the 18" Continentals are rated for 3640 so this is a total of 7280.
Now Ford would love to call this a 7280 pound rear end and leave the competition even further behind.............but they can't, some component is keeping the rating at 7000.
One last point on weight ratings, before I talk about hitch placement.
Your axle ratings, front and rear always add up to more than your gross rating.
This is a safety margin I would not ignore. Going a little over your GVWR is no biggee.
Going over your axle ratings is not a good thing.
My own example, My truck's GVWR is 11200. My rear axle is 7000, front is 5600 so total is 12600.
On hitch placement I have installed the hitch that I own now on my last 3 trucks.
http://www.hijacker.com/
has very good instuctions on hitch placement. Fifth wheel hitches are installed with the pin centred over the rear axle or up to 3" in front of the axle. Mine is about 1/2" in front.
This is for optimum handling but I have talked to people who have mounted hitches aft of their axle centre to get more clearance on a short bed. I don't agree with this nor do the hitch companies but even in hitch installations we have people that think specs are only guidelines.