Yeah, you change how much weight is distributed off the rear axle of the truck in two ways.
Changing the number of chain links on your chain is one way. You do that if you don't have about 50% of total tongue weight on the rear axle of the tow vehicle with the WD hitch adjusted. Loosening one chain length will put more weight on the rear axle. Tightening one length will take more weight off the rear axle.
Your goal is about 25% of total tongue weight distributed to the trailer axles, and another 25% distributed to the front axle of the tow vehicle, leaving about 50% of total tongue weight on the rear axle of the tow vehicle. You change the percentage of tongue weight being distributed to the front axle and trailer axles by adjusting the angle of the head of the WD hitch to the coupler on the trailer tongue.
If you don't have any rig weights yet, and you don't have a tongue weight scale to get total tongue weight, then you need three trips across the CAT scale:
1] total rig with WD spring bars tightened.
2] Total rig without the WD spring bars tightened
3] Tow vehicle (TV) only, no trailer.
Gross vehicle weight (GVW) is the weight on the two TV axles.
GVW with trailer without spring bars tightened
minus GVW TV only
Difference in front axle weight, rear axle weight, and trailer axles weight, with and without the spring bars tightened, divided by tongue weight, = percentage of tongue weight distributed to the front and trailer axles and off the rear axle.
Tongue weight 650 pounds
Without spring bars:
trailer axle 3480
With spring bars:
trailer axle 3620
Ignore the 20# scale error
Front axle difference = 3280 - 3040 = 240 = 37% of tongue weight = too high.
Rear axle difference = 3880 – 3520 = 360 = 55% removed from rear axle, leaving 45% still on the rear axle = close to the 50% goal.
Trailer axles difference = 3620 – 3480 = 140 = 21.5% = a little bit too low.
So we need to adjust the angle of the hitch head (and ball) to the coupler to distribute less weight to the front axle and more to the trailer axles.
Grumpy ole man with over 50 years towing experience. Now my heaviest trailer is a 7,000-pound enclosed cargo trailer, RV is a 5,600 pound Skyline Nomad Joey 196S, and my tow vehicle is a 2012 F-150 EcoBoost SuperCrew.