Respectfully, I will disagree with those who say you don't need a WDH with a 3500 lb trailer. I am not saying, though, that Ridgelines can use a WDH. In other threads, there are many Ridgeline owners who say they use them.
The reason I recommend a WDH is that they balance the entire "rig". When you put 350# - 525# on the ball on most SUVs or half-ton pickups, the tail drops significantly. This un-weights the front axle, reducing braking and steering capability of the front tires. Not a big deal on dry pavement, but a big difference in rain. Plus, with the dropped tail, your headlights will aim into oncoming drivers' eyes at night. Not only is that discourteous, but it is also dangerous.
I tow a 3500 lb trailer with a Grand Cherokee with the tow package, and it makes a world of difference having a WDH. I did not have one initially, and won't tow without, now.
My opinion. Do with it what you wish.