[Elecraft] Grounding question on remote tuner

[Randy Cook]

Weather damage repair time. I am rewiring my ~84 foot inverted L antenna system, Up a SpiderPole about 31 feet, out about 53 additional feet. Still tuning length. 
I have mounted a remote MFJ tuner on a post about 3 feet from the antenna base. Antenna wire goes down the pole, connects to 4:1 Unun input lug, then goes via coax to tuner. Out of the tuner to a long coax run to my shack. Choke at the rig end of the coax run.  
Radials mount on ground connection lug on the Unun. 
I was a bit confused with the tuner wiring. The manual says to connect ground lug to the ‘system ground’, I assume that means the radial collection point. But, isn’t the tuner already connected to the ‘system ground’ via the coax shield? Is it necessary to run another wire from the tuner ground to the radial connection ground?

Thanks in advance for any advice.

73
Randy - K6CRC