Well, since I need to make my own shroud for the 2,7 anyways (its VERY wide and the Oettinger cylinders are quite some wider as well) and the case has been cut for the Ahnendorp system may many moons ago, I have started sculpting class:
Here's a picture of a RMB shroud with an even more pronounced 4th cylinder air path:
More pics in the next post: