I've heard really good things about XPS ribs also. But you're right, they have quite a bit less load capacity than the Westlake tires. The ST235/80R16 Westlakes have 3,520 pounds of load capacity. The LT235/85R16 Michelin XPS Ribs have a 3,042# load capacity. That really concerned me until I remembered that the axle weight rating is 6,000 pounds on my 337. If the load was equally distributed on both tires, I'd have 6,084 pounds of tire load capacity on my 6,000# axles. That's cutting it close, but I am no where near the max weight on the coach, so I'm not too worried about it.
One interesting tidbit about the Westlake tires that I'd never noticed before. They have a speed rating of "L" which is 75 mph. This is actually stamped on the side of the tires. I'd always assumed they were limited at 65 mph like 95% of the ST tires out there.
Jim