Car running hot would it be a good idea to switch to HHR fan?

just judging by the picture of your current fan set up, it looks like atleast a third of the radiator is not being used. As in the shroud covers up a great deal of the surface area of the radiator. If the car doesn't cool while driving down the highway it leads me to believe either the radiator is not efficient enough, or its the lack of airflow thru it. When driving down the highway you will have more than enough airflow to keep it cool even without a fan. I would put money on the current shroud causing your problem. Just my 2 cents.