Dunno about twin axles, but the ALKO info gives the shock absorber length when the axle is unloaded (ie hanging down when the van is jacked up)and the distance between the axle centre line and the top shock absorber mounting.
For all colours the shock absorber length is 255mm eye to eye and the top eye to axle centreline is 265-270mm for Green, 235mm for blue and 265mm for both red and black. So if you use a ruler you should find the optimum hole. Mines a red shocker but fitted to a single axle van and using a ruler the optimum hole was the middle one.