x3 to both tuning the antenna, and avoiding the "no ground plane" antenna, and putting it as high as you can. If you used the mount in the picture, but put the mount just above instead of below the tail light, and the cap is fiberglass, it wouldn't work half bad, I don't think. Longer and higher is better. Make sure the coax shield/antenna mount is grounded to the truck at the mount.
Also, if you can find a ham that has an antenna meter, they can help tune your antenna in just a few seconds. SWR meter works fine, but something like an MFJ-259 is easier and faster. Not worth buying one to just tune 1 antenna, though.