In order to completely get rid of this jitter/bounce, we had to do three things. First, we had to increase the belt drive ratio to 2.5:1. That help quite a bit, but what we also had to do was go to the MKS servos. The reason for the latter is that after an exhaustive and expensive series of tests, it turns out that in addition to having 12 bits of resolution in the servo electronics, what is also needed is a really low deadband timing rating. This characteristic alone seems to have the greatest impact on just how smooth you can get this setup. Otherwise excellent servos, like various hi-res models from Savox, JR, Hitec, and Futaba, simply don't work as well in this application because they had deadband values around .002ms. The MKS BLS950 has a deadband value of only .0008ms. The only other servo I've found that is similar in this regard is the $200 BLS series from Futaba. Finally, the last thing we need to do is use a gimbal controller that lets us set the PWM rate to 500Hz. I've done tests to keep dropping this value down, watching what happens, and as soon as I get below about 300Hz, the jitter/bounce is back..