Thanks Brian. I talked with that farmer today; upside is great carrying ability and can be added or removed in about an hour. Are a number of questionable things about them. About 12 mph max roading speed. Cost obviously. Ability to turn well. The rear wheels in super soft conditions will sink deep. And in heavy load conditions, I wonder if final drive output axle shaft may have more stress and failure potential than using tall single tires. His are Grip Trac brand, and they just bolt onto the final drive just like wheels do. Track on the ground is about 8' long. He always makes "A" shaped turns which would be tedious and time consuming. I will research more. Doug