I have a Pro-Eagle 1000lb WDH setup that the dealer installed on my original tow vehicle (a Sienna Minivan).
The hitch with the WDH spring-bar sockets bolts to the extension coming out of the receiver on the tow vehicle. With the van, the ball was actually higher than the receiver (so instead of the hitch dropping to be level with the tongue, it rose up).
When I got the Tacoma, I un-bolted the hitch, flipped the extension over to make it a drop instead of a rise and re-adjusted the ball height so the Tacoma matched the trailer. There are 4 or 5 holes to adjust the hitch in any increment you need and for more drastic adjustment you can flip the whole extension bar over if needed.
There's a picture
here that if you look carefully, you can see the adjustment holes on the hitch where it meets the shaft that goes into the receiver.
With my Sienna I had airbags and usually had the WDH springs with 5 links of tension.
With the Tacoma I still prefer to use the WDH, but only need to go with about 3 links of tension on the spring bars to do the job.
With less tension required, there should be less weight being transfer between axles.
Not sure, but the Tacaoma 4x4 with Elkmont combo could probably benefit from *some* weight distribution.