WD hitch specifics

rbpru wrote:
We know that if I added another set of springs to my F-150 I could stiffen the suspension and increase the tongue weight.

I wouldn't say you can increase the tongue weight that way, at least not "Officially". You would improve the truck's handling of that increased tongue weight though.

There is a limit of course because the remainder of the system, the bearings, brakes, frame etc. remains the same.

Yup.

Ford says the use of a WD hitch increases my particular truck’s max trailer weight from 5000 lbs. to 9800 lbs. hence the permissible tongue weight would rise from 500 lbs. to 980 lbs. In effect by adding two torsion bars I have stiffened the suspension shifting some of the weight to the front axle and a portion of the weight to the TT.

I don't think it "in effect" stiffens the suspension. It just transfers weight from the rear axle. This better balances the weight on the truck's two axles improving the ride. You could well want a stiffer suspension with a WDH, at least I did. IMHO the stock F150 suspension is stupid soft, only good for unloaded driving.

The question is, do the torsion bars increase the vehicles “max cargo weight” by any more than the amount transferred to the TT?

From what I understand it does not, max cargo is max cargo.

Yup.

I am also curious as to what percentage is transferred to the TT.

In my case only about 12% of TW, but I believe that Ron Gratz has said 20% on average. So I guess "it depends".