Like I said, the way I currently have it reduced temps by 12 degrees after 15 minutes of bashing around the yard. I am going to remove those small PC memory heatsinks and replace them with two of
these, again mounted with thermal epoxy. That should reduce temps even more. I hate using a fan because it adds wiring complexity (albeit small) and it's just one more thing to break or wear out, which is especially bad if you are counting on the fan to keep things cool. I'd rather keep it passive if at all possible and arrange the fins so airflow runs through them. Swiss-cheesing the sink should work as well too - I'd use holes no larger than 1/8" and have 1/8" spaces between them. The idea is to create as much exposed surface area as possible while keeping enough mass in between.