You shouldn't run the ground from the mount to the tub. What kind of mount did you by? If its painted grind some of the paint or powder coating off where the cable connector attaches to the mount and where the bolt goes into the tailgate. Only sand the mount. You want to make sure you have good conductivity. This causes the mount to ground to the tailgate. Then you want to ground the tailgate to the main vehicle.
This is the correct way and the best way for optimal transmission.
I am having a HUGE ground problem so when googling this issue I ran into your post. I have one question. Why is that the best way?
I was trying to over-do the ground, so I took my TeraFlex tailgate mount and scraped the powder coating off at the coax connection, and where I drilled a hole for my ground wire. I used 12 ga wire and ran it through the plug and under the horizontal plastic, along the black strap and behind the plastic at the back. I attached it to one of the bolts. It was good, but not great. I ended up drilling a hole, sanding it and screwing the wire to the tub. It was good, but not great.
SOoooo. I ran a jumper from the tie down bold on the floor of the JK to the screw that I put in the tub. I am now getting .1 to 0 but I still can't get a good swr.
You say to ground the tailgate,,, isn't what I did overkill? and wouldn't it be even better? I'm going crazy trying to get this nailed down.
To make matters worse, it appears that the multimeter reading goes from .1 to 10.0 when I power up the CB.
Why in the world would it do that?