I think the guys reasoning may be right. If you think about the surge brakes,the coupler has to come forward on the ball right? If you have the WD bars on the frame of the trailer,It makes more of a ridgid connection. I don't know if the trailer would slide forward enough to set the brakes. I could be way off though?

I tow a 21' Bayliner Capri,it's weight across the scales is right at 4000lbs. I have a Chev 1500 and it does sink the rear end,but I don't think it's more than an inch. Our travel trailer is 23',and weighs just over 5000lbs. When we have it loaded for a trip we have about 12% tounge weight,and thats about 600 lbs. I can't remember what it drops the rear down,but it's probably close to 2" or so.
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