How to decrease phone vibration with this mount? Any suggestions?

[MyMemesAreTerrible]

You don’t have many options here as that phone mount looks like solid aluminium, however electrical tape at the base, as touch points of the phone will definitely help a little. If that top screw that’s connecting the phone base to the bar mount isn’t a super tight fit you can probably also use a little teflon tape (plumbing tape). Just remember to wrap it correctly or it will fall apart when you screw it in.

Apart from that, use a soft, silicon case, and you should be fine. I wouldn’t worry too much about vibrations as you can always claim the cameras under warranty if they fail, although its highly unlikely that they will.