If you have wires going trough yaw, you need a slip ring. When there is nothing mechanically limiting the yaw movement use RC speed mode and you have what you want.

Greetings from Bulgaria !
If you use the slip ring will appear in the video signal interference. This can lead to loss of information OSD after mixing video signals. There may be loss and PWM signal. Engines gimbal make harmonic waves that affect your video and PWM. I have not noticed weathered signal in S-bus.
There slip ring with coaxial cable + 12 cable - price is higher.
http://www.aliexpress.com/item/Slip-ring-SDI-1080P-1080I-12ring-1-RF-Collector-ring-CCTV-monitoring-slipring-High-speed-signal/32294422558.html?spm=2114.01020208.3.17.sJZei5&ws_ab_test=searchweb201556_2_79_78_77_91_80,searchweb201644_5,searchweb201560_9

Excuse me for bad English, but I want to help. If my tone is bad - sorry! Use online google translator.

Certainly better video transmitter to be placed under yal.
My configuration does not allow. I have DJI S900 with A2 avl58, OESD mark2. All these components communicate with the controller A2 by Can bus DJI.
Management gimbal, use basecam 32bit. I achieved good results, but use Sony video camcorder, zoom as manage the land. At full zoom (optical X32) has a slight oscillations in flight. When the drone is on the desk or shake hands, picture perfect!
I guess soon I'll be able to show perfect picture at full zoom and to share this with you.
It helps me a lot tool for analyzing the gimbal - basecam 32bit.