I have a four-link on my sled, but that is so I can set the frame on the ground with the airbags. The four-link does well except on an uneven surface (like a parking lot entrance). I get a nasty wiggle from the rear of the truck accompanied by squeaking.

The frame is boxed and notched for rear axle clearance and I added two tube crossmembers to support the fuel tank in the rear, so there is little-to-no flex in the frame. The "give" on an uneven surface is absorbed by the four-link. I'm sure this is leading to premature wear and a possible risk later-on.

I always inspect my suspension when the truck is in the air for maintenance. I also built a set of bolt-in bumpstops for use if the air ride system fails (so I can get home) I keep them and the wrenches to install them in the tool kit.

Sorry for rambling, bye...