Three-dimensional renderings of the three different model clusters analysed in this work. All clusters have the same stellar content listed in Table B.1. The size of the sphere is scaled by wind power. Magnetic stars are marked in red. The lines indicate the orientation of the magnetic axes. Clusters I and II have the same compactness R_c = 0.6 pc and only differ in the spatial distribution of stars. Most notably, a rather powerful magnetic star is located close to the centre in cluster II, while in cluster I, it is at the outskirts. Cluster III is less compact, R_c = 1 pc.