There is some wording behind the sentence missing. You can rotate the radiators as much as you want around the Y-axis.
I have updated the files and MFlow on the Challenge page. The guide parts have been updated around the engine cover volume, so that part is new and gives you more freedom. MFlow has seen some upgrades as well. I did some tuning on the CFD settings so they will affect your results and I recommend to use this new version which will also be the version used for the first race.
I hope today there will be a new version of the rules clarifying some of the questions you guys had and some things Richard and I spotted.
Also Richard is aiming to get the new version the the Virtual Stop Watch done soon.