There is a page on the 40m wiki explaining the procedure.

  http://blue.ligo-wa.caltech.edu:8000/40m/OSEM_adjustment_proceedure

Additionally there are several old elogs about the cross-coupling minimization, which can be useful for us:

[1] "SUS ranking from measured data", iLog by Osamy (Aug.22 2005)

[2] "TF from position to sensors for ETMX ", iLog by Osamu (Aug.25 2005)

[3] "Further OSEM tweaking", iLog by Rana (Oct.3 2006)