Actual Weights as measured

The weight on the hitch itself is not removed from the hitch but it is removed from the TV rear axle. Think of it this way:  in a statics problem (where things aren't actually moving around) all the forces have to balance to zero and all the moments (separately) have to as well. If the forces don't balance then things would rise up or sink down and if the moments don't balance things would rotate. 

The weight of an object is of course a force pressing downward and is countered by an equal and opposite upward force from the ground.   So, since tensioning the wdh applies moments which are balanced by increasing forces pressing up from the ground at the front axle and the trailer axle, then there has to be an equal reduction in the force pressing up from the ground somewhere else, because the total force pressing up by the ground has to equal the total weight of the rig, which isn't changing. That somewhere else is the TV rear axle.  So the downward force on the hitch itself doesn't change but the downward force on the rear axle does. The front axle load gets higher and the rear axle load gets lower, both of which are good things for your TV.  

There are some downsides though.  There is now a new downward point force on the trailer frame from the tensioning chain/bracket, and there is more load on the already heavily loaded trailer axle. And there is also a moment placed on the TV receiver and frame which wasn't there before. So the tow vehicle and receiver have to be rated for a wdh and the load of the trailer and hitch have to be within those specs. The trailer frame and axle should be rated for the additional load too, which is where axle and frame reinforcement come in. 

Such a great discussion.  I'm living in the "moment".

Based on documented failures, isn't the weld from tongue to frame one of the most significant points for potential failure?  That being the case, I was considering adding reinforcement there as you would not have to give up any clearance on the bottom.  I did examine the weld and it looks pretty crappy.  A shimmed piece of angle properly welded would significantly increase the strength in my unqualified opinion.

I was also going to weld the bolt-on receiver as it tends to flex with the WDH.  I just have to confirm I can still remove my Jeep bumper.

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My 179's tongue weight is closing in on 550 with full fresh water, dual GC2's, one (not two) full propane tanks, and not much of anything else heavy forward of the trailer axle. Total weight is about 3800 so that's around 14% tongue weight. So yep, as Podwerks says, FR's tongue weight numbers are really not anything like the real world for anyone who does much boon docking with the bigger rpods.  

You have to be careful though too about moving too much weight aft. If, like me, you are returning with all that water moved to the 179's gray water tank that reduces tongue weight percent to about 11. Get much lower than that and the trailer can be sway prone, so there is a sweet spot for me around 14% outbound and 11% inbound.