One, single, large antenna on a properly grounded mount will work
better then any attempt at co-phase on any vehicle not 8.5 feet wide.

At 27 MHz, any antenna shorter then 5 feet is a waste of time.

rab wrote:

I've got an older ford crewcab with a radioshack ssb cb radio. What
would be a good antenna setup for this rig. I will be hauling an
overhead camper on occasion. Twin mirror mounts apeal to me. What is
going to get me the best all round performance?

Thanks