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By the way, your user name, "GroundURMast", is that a recommendation that improves performance or is it a safety thing?
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Safety first... Best practice. When your antenna system is grounded correctly, you protect the tuner from static discharge damage and you also would expect to be able to conduct enough current to ground to be able to trip a circuit breaker if power from a branch circuit accidentally contacted a part of the antenna system. (A nail driven through power and coax... Christmas light cord frayed... etc.)
I've heard arguments for grounding based on 'reduction of interference'. The technical support for that theory holds up in the LF, MF & HF bands where wave lengths are long and so the antenna down-lead is often a small fraction of a wave length. If so, grounding the down-lead shield can effectively reduce RF voltage on the outside of the coax and thus reduce the possibility that the coax shield would act as an unintended antenna element.
In the VHF and UHF bands, wavelengths are much shorter, so grounding the coax shield does not provide a continuous low impedance along the full length of the coax (presuming it's more than a few inches long... in fact just 1/4 wavelength from the ground point (presuming it's an effective RF ground) you will find a very high impedance point where a high RF voltage could be present despite the ground just inches away. The bottom line is, an antenna is connected to the coax... the antenna is going to receive interference if it's present and couple it to the coax.
http://forum.tvfool.com/showthread.php?t=901