This was by no means my idea. It was pulled from the cooling issues thread that was previously started quite some time ago.
I have experienced some slight overheating while driving on the highway after extended periods of time with ambient temperatures of 85 F or more. My previous set-up is a pusher fan that runs at all times, a PWR civic duel core radiator, a Honda thermostat, and Honda Genuine coolant. This has worked very well for me in most other cooler conditions.
The new set-up is very similar but, I have added a custom cooling plate to block the open half of the radiator support for airflow redirection towards the radiator. It was extremely simple to make and took only about 30 minutes of my time. I used A/C ducting sheet metal for the plate and some simple hardware. The reason A/C ducting metal was used is because of its resistance to rust, ease of cutting, and cheap price. The piece used in the pictures below is ~ 14.75" x 9". I have also substituted my Honda coolant with distiled water and Water Wetter. Everything else has remained the same. On my ride home today in 85+ F the car was great. I spent about 40 minutes on the highway at 75mph without the temp gauge fluxuating at all. I also did not need to run my fan the entire time coming home except for slower traffic situations.
Now here are some pics of how it is installed. I hope they are helpful.
Just for fun 
Sorry about the cruddy engine bay. The car sat all winter and I’m still in the process of cleaning it up for the car show season. Hope this helps give people some ideas. 