Have a read of this as it shows that the cube black doesn’t have great vibration damping characteristics below 120Hz, the range in while larger multis operate in. I’ve had similar issues to yours where no amount of mechanical tweaking could fix the issue, so I put on one of those dampeners which consists of 2 plates and 4 grommets sandwiched in between and that made a massive difference for me. Went from average vibrations of approx 30 down to 4.