Sorry, I don't understand what is meant by "unsprung weight". If a person weighs 200 pounds, using double wall 32-36 spoke wheels probably is in order for a loaded tour. If a person weighs say 150, why would that person need such a robust wheel to haul the same weight? Doesn't make sense to me. Also, a person at a heavier weight will require and use more energy than a lighter person. Every pound (or ounce) that has to be moved requires a certain amount of energy. I know this firsthand, since I learned that lesson cycling up the Coquihalla in BC. I didn't think that weight was an issue, because you're just riding a bike. We just take it for granted. Ha! I was probably 198 pounds at that time with 46 pounds of bike and water. I have a road triple 52-39-30, and ten in the back (36 on down). Gearing wasn't the issue. Just ran out of energy (and water!) Bad day, but I made it thru it. As mentioned earlier, most of the group that I went with across Canada only had single wall wheels and 25's, but we weren't loaded beyond what was needed on the bike that day. They were way faster than me. Way faster. Lighter physically, and lighter bikes.
One guy heavier than me riding a cross bike that had single wall wheels and I'm pretty sure with 24 spokes, split his rear rim twice which had to be replaced obviously on the road. One of the times it split, he road nearly 700 kms on a tacoed wheel. Pretty amazing feat I have to say. Sometimes you gotta roll with what you got!