#1 You have choosen to use a Weight Distribution Hitch.
#2 This is not about wether to use one or not, This about the generally accepted method to setup and apply the hitch.
The first step is to establish the height of the towball coupling on the caravan.
1st We need to level off the caravan, position the van on reasonable level surface, then using the jockey wheel to raise or lower the front of the van untill it looks level. This can be confirmed in 2 ways either by a spirit level or measuring 2 points at the front and rear of the van. Measure the height of the coupling and record that ie 400mm.
Now position the tow vehicle in line with the van and check the height of the towball, measuring from the ground to the top of the towball it should be between 400-410mm. I neccessary adjust the hitch to the correct height.
2ndPosition the the tow vehicle with the towball directly under the tow coupling ( dont lower the coupling to the ball)We need to measure the suspension heights on the front and rear at the top of the wheel arch, with these 2 numbers recorded, lower the van coupling onto the towball fully taking the weight off the jockey wheel. Now record the tow vehicles suspension heights again and record them.
3rd Time to engage the lift or spring bars, start with 4th or 5thchain link, when both are locked in place remeasure the suspension heights, the prefered height at the front suspension should be as almost the same as the first measurement +10 to 20mm is ok. To get the suspension tobe within that range add or remove 1 chain link at a time, if you need to fine adjust the number of links and make 1 link a ˝ link add a bolt to a middle link.
After you have the the tow vehicle at the correct now is the time to check it caravan is level or slightly nose down, if the caravan is too low at the rear, you may be able to adjust the ball angle towards the front of the caravan to lower it, likewise tilt ball angle away from van will lift the front.
After you have got to this point, now is the time to visit a weighbridge check all your weight are within the limits.
Almost every manufacture of weight distribution hitches sold in Australia recommends 100% return of front suspension height, commonally refered to as FALR (front axle load return), except one Haymen Reece USA recommended 50% FALR only one model in their range.
Now a word caution, this setup process is best done with both your tow vehicle and caravan fully laden as if you were departing on your trip, and if you alter the load in either or both vehicles later on then repeate process again, ( I found out by first hand experiance when I added 60kg to the tray of my Ute, that the quick fix was to tighten the lift bars by ˝ a link to get to safe and level place where I could make the neccessary adjustment aand that was to raise the hitch head one hole and increase the angle on ball by one turn towards the caravan)
I hope its not from SAE J2807 because that has been debunked
I got it from the installation directions for the WDH.
I doesn't take much brainpower to realise that if you adjust the WDH to recover 100% that with every bump, pothole, gutter etc. that the instantaneous setting will be over 100% which is not a good way to treat your car or van.