I have had 3 rigs with 5100's all of them on the 3rd setting. I tow a boat alot or I'd do the 4th. The ride is awesome from the 5100's! I would say something is wrong if you notice a big difference in ride between the 2nd and 3rd notch.
I added 5100's this week. 3rd setting. Also 275/60r20 cooper AT3 4s tires. Like the setup. Much better ride and handling compared to the stock Ranchos.
So far so good. No issues. I would buy it again. I live in MN so I liked that even though it has the flat profile like the Bak it has velcro down the sides. I think that will be better than the Bak for my climate.
Got my new Truxedo Sentry CT hard roll up installed last night. It's a brand new cover for them that has a canvas top rather than the shiny vinyl. It's got an almost flush profile. So far I really like it. Not cheap but seems worth the price. I will report back if any issues come up.