Dependencies of the difference in the distance measurements for our clusters by comparing the co-moving fundamental plane distances with the co-moving redshift distances on the co-moving redshift distance itself and the number of elliptical galaxies per group. Top-left panel: all groups that contain at least one elliptical galaxy. Top-right panel: all groups containing at least two elliptical galaxies. Bottom-left panel: all groups that host five or more elliptical galaxies. Bottom-right panel: all groups hosting at least 10 elliptical galaxies. The solid red lines indicate fits on the displayed data, which show an increasing dependence of the ratio between the fundamental plane distance and the redshift distance on the redshift distance with an increasing number of elliptical galaxies per group. The dashed black line only provides a reference, if this trend was not detected.