A mastery bridge fits in the sockets tightly, and doesn't rock back and forth. The Mustang bridge rocks back and forth the same way the regular bridge does. I find that the problem is that there's nothing to determine with any real precision where the "center" point is, when setting the bridge up, and it's been impossible, in my experience, to adjust the intonation without pushing the bridge out of it's "center" position- making precise intonation nearly impossible to achieve. Then there`s the problem of the bridge "falling" backwards or forwards in the middle of playing something, and the difficulty of "centering" it in mid song. I've solved these problems by intonating the guitar with the bridge pushed all the way back, and leaving it there. The vibrato still works very well, as I mainly use it to bend things down, anyway, and if the bridge migrates forward while using the vibrato, I can just pull the bridge back with relative ease, even while playing.
