I operate portable from my car regularly as a Parks-on-the-Air activator. My main antenna is a Chameleon Hybrid Mini unun on a mag mount with a 213" stainless steel telescoping whip. I get great results on 6-20 and good results on 30 and 40. On 17 and 20 I regularly reach Europe and South America from Central Florida. One interesting part of this set up is the coax that comes with the mag mount is unused. It's on the ground side of the antenna and I typically just leave it rolled up in the back seat of the car. It was suggested by the manufacturer that I cut off the PL-259 and attach the conductor to the frame of the car (like a seat bolt that attaches to the uni-body). The theory is that it will cause the body of the car to act as a ground plane which will increase performance. Instead of ruining the coax on the mag mount, I attached a barrel connector to the end of the PL-259 and attached a 3' coax jumper to the conductor. I then attached the other end of the jumper, via an alligator clip to the car's frame. I haven't noticed any increase in performance. In fact, the SWR on my Kenwood TS-480SAT has gone up. Should I do anything with the coax from the mag mount or just go back to tossing it in the back seat of my car? Thank you and 73!