I have an RV and an ES. When RV8 guys put the 200hp Lycoming in their planes, they had cooling problems. One interesting way they dealt with it was to install a louver vent on the bottom of the cowl similar to your heating vent at home. This vent had a sliding plate on the inside to open and close it. It produced a nice low pressure pull when open and very little drag. It was also easy to install. Just a thought.
Chat Daniel
Super ES N891AC
RV8 891AC