Hello scherbenreich,
I've been using coolbook on 3 MacBooks and 2 Pros and so far I can say it's definitely a gem! The lowest setting on each CPU is different, that's why the default setting is high, in order to include even the worse of CPUs, regarding voltage. You should try running the test application found in coolbook's website on the setting you found stable for a couple of hours to see if it works ok too. If you get any errors, you should ramp up the voltage by one click. Generally speaking, you should keep the one setting higher than the one that passes the tests, just to make sure. You should also add settings for the other speeds of your CPU. I believe that sensitivity set to "high" would be perfect for you. You could also try limiting the temperature (the CPU speed will drop to keep it down) however I don't know whether it would be OK for your applications, you could experience video shuttering or something.