When do you actually need a WDH?

This is one of my points of interest during our travels. We've seen 1-ton duallies towing 20-25~ft TT's with WD hitches. We've seen 3/4 tons towing 30+ ft TT's with just a ball. The only ones I've seen wagging like a happy puppy were SUVs towing TT's even with WD hitches. The thing to keep in mind is leverage. A 156" wheelbase pickup with it's ball 60" behind the axle and 500 lbs of tongue will take 192 lbs off of the front axle. That 192 lbs gets added to the rear axle. So you've really added 700~ lbs to the rear axle. Same with 5th wheel hitch placement. Seen many mounted as far as 18" behind the axle. It depends on the truck and pin weight or tongue weight how far you can take it. Too many variables so manufacturers have to make blanket loading and hitching recommendations to cover their tails and keep their customers safe. Axle to pin or ball in inches / wheel base in inches x pin or tongue weight. Sum comes off of front axle and gets added to rear axle.