I favor SumoSprings over airbags for the same reason. I've actually run them mostly in front applications for a plow truck and GM passenger vans for the fleet I manage, and will keep purchasing them. They are not harsh, even with the most heavy-duty rated option. I haven't used Timbrens so can't compare.I saw another product called SumoSprings……….anyone have hands on experience with them?
Air bags are appealing but seems like the bags and lines are more prone to leaks and failing...…....and the need for an air source
Edit: I ended up using long add a leaves on my Sierra, and am pretty happy so far. I don't have a topper and usually only have 100-300lbs in the bed, and the ride is not rough by any means. They don't squat too bad with my horse trailer or flatbed trailers I've pulled. I actually removed the factory blocks when I installed the add a leaves, since I didn't want much extra height. I'd say the bed is about .5" taller than stock this way.