Very simple alignment (manual linear x direction shifting only, no rotation, assuming equal z spacing) and tracking.
Reference plane = Module 3 (~center)
Deviation calculated from track prediction using the other layers.
Simple Center-of-gravity algorithm (as of APVDAQ_Analysis), no eta applied.
Using only events which have exactly 1 hit per plane (~80% of all events).

Results: 
 Residual RMS = 4.99 um (REFERENCE against neighbor layers 2+4 only)
 Residual RMS = 6.35 um (REFERENCE against all 7 other layers) -> needs more sophisticated alignment