Spring bars at or below tongue weight? That is an opinion and mine is the polar opposite based on actual experience.
Speaking for nothing larger than 1/2 tons, I have found on repeated occasions having WD bars at or below the ton weight results in poor weight distribution and a soft rear end. This gets people looking at bags and helper springs and does not help handling.
I run 1400 bars with a Hensley and 900+ (max weighed was 960lbs) tongue on my SUV and could not be happier.
My camping buddy was running 1000lbs bars with his F-150 with exact same tongue weight (high 900's) and complained he was tensioning the bars too much (was upto 7 washers and was hard to connect) to get weight back on the front wheels. A new WDH with 1400lbs fixed it and the rig drives as he expects now.
Many years ago I towed with a Honda Pilot and it too was near max. I ran 600lbs bars with a 400+ tongue weight and it did ok. Then I bumped to 1000lb bars for cheap and WHAT A DIFFERENCE!
It's poor advice to assume the WD bars should be at or below tongue weight for every tow vehicle.
IMO, 1/2 tons and less, always round up to the next size bar. There's actually no reason not to. Rounding up just one size will not result in a harsh ride, doubling what you need would! Handling will be what it should be and you wont need to think about air bags and helper springs because the WDH is doing what its designed to do.