Is it possible to have (too much) antenna?

In your situation where you would have the loading coil sandwiched in-between your truck and reefer unit, yes, it will hurt your CB's performance. It doesn't have to do with how big the antenna is, it has to do with the application.

 

I gotcha.


What if the antenna was mounted on the drivers side mirror?

 

I think it would perform better than what you've got now. Be warned that trying out new antennas and comparing them can get expensive! There's always something bigger and better out there.