3- and 4-inch swami belts from about 1980. I used the top one regularly for about 7 years.
At first it was just a rope, but soon a bowline on a coil became common, which is much more comfortable. about 6-8 wraps of line were taken around the waste and cinched off with a modified bowline tied around the coil. It wasn't that comfortable, it consumed about 25 feet of rope (pretty significant if both climbers did this), and was time consuming to get on and off the rope.
Climbers started wrapping webbing into a wide belt, but the width was hard to control and after shifting or falling, was often no wider than the webbing. Soon, climbing shops started producing fleece-lined swami belts 3-4 inches wide with accessory loops. You lashed this around your waist with 1-inch nylon webbing. It was more comfortable, and so long as you were young and had strong core muscles, tolerable in gentle falls and hanging for short periods. Better than a chest harness, anyway, although that seems improbable. I swear, based on many experiences, it is true.
Interestingly, they never got wider than 4 inches. It didn't seem to help must and got combersome. Soon after these were developed, shops started making leg loops to go with them, and thus the modern seat harness was born.
I tape large stiff foam pads inside the leg loops of my harness if I'm going up the mast for a long while. It really helps.
The ISO standard for sailing harness in 45 mm (1.75 inches), and most are this width. This is also the standard for rock climbing harness and automotive seat belts. However, most rock climbing harnesses have leg loops 2 inches wide and 3-inch belts. Racing seat belts are 3 inches, with 6 belts instead of 2.
While a full body harness is what you really need to take a huge fall, that's just not practical. But could a chest harness be improved by making the band wider? A very simple thing to do.
I should have started from scratch, but I'm down to a writer's meager income, so I reworked an old harness I had. Though it has some rust stains, it hasn't been in the sun much the webbing is far stronger than the code requires. By removing some hardware, resewing a few things, and adding a fleece lining (why not--it will feel good in the summer), I increased the width from 45mm to 70 mm, or 56% more area. Yup, it feels better when hanging, though it is still horrible, like any chest harness.
Stiffer webbing would help. No, it is not adjustable; it's just for me and I have another for winter wear. Loosing the buckles makes it lighter and more comfortable.
I will be testing 45 mm, 3-inch, and 4-inch straps for an up-coming article. However, I know there is a limit. Even being hoisted with a well padded LifeSling really stings after a few minutes, so don't expect miracles. But if it saves a few bruises or a broken rib, it's a big deal. I'm thinking 4 inches would be a sensible standard, but let's see what the tests say. As near as I can tell, the design of the straps and buckles makes no difference under load, only the width of the strap.