Reddit reviews XCEL Closed Cell Sponge Rubber Pads, Various Sizes to Choose from

Well it's not quiet to be honest but you'll have a hard time dampening the noise no matter how you go about it, I do recommend getting vibration dampening cube thingies (like this or maybe this) to put under your rig just so the noise won't travel into the floor which will make it exponentially louder. Those anti vibration things also help keep the vibration in the rig rather than dispersing it into your surrounding area.

As for structural integrity, I've had no issues. I got a tube of threadlocker in case the screws would vibrate loose but I haven't put it on yet and they are still as tight as the day I put them in so I wouldn't worry too much.